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*The front courtyard and the central courtyard call to mind.

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*An intriguing way of thinking about private open space: Private open space is really no more than another room in the private domain - roofless perhaps, but within the private domain, and not part of the protective-presentational boundary. In the central courtyard house the court is a plein-air living room; in the front courtyard house the court is either a plein-air entry hall or living room, depending on the floor plan and the occupants.





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*We do not know how freely one entered the Parthenon at the height of Athena’s reign, but today the Acropolis is a park in which the buildings are as easily entered as the rest of the grounds. The fora, too, may have been more restrictive than sometimes assumed - current conjecture seems to be that the Romans were more than the Greeks in the habit of limiting entry to their fora by profession and class.

building blocks

the gateway - or boundary:

It will be helpful to start this analysis with a relatively simple form of urban agglomeration, and to identify some of its key spatial and territory-defining elements. With this understanding we will be able to think more clearly about relative territorial position, and about some more complex urban forms which build on the logic of the simple village.

A typical single-street agricultural or trading village is constructed along a roadway. Small buildings sit facing each other across the “street”. And the space defined by these buildings becomes the public space of the town. What we usually call the “fronts” of the buildings line the street, and act as the gateways between public and private realms.

This gateway is a key boundary in the urban framework; it has three primary “duties” in relation to space, ownership, and understanding of appropriate position: 1) it presents the building/owner to the public domain; it protects the building/owner from intrusion by the public domain; and it defines, or clarifies, to those on both sides of the boundary where the public can move freely, and where the public is to come only by invitation. This is a key concept, and in order to discuss this functional gateway/boundary through this argument, I would like to call it something; I would like to call it what it is: The protective presentational boundary.

The image which comes to mind when thinking about this boundary will vary with different cultures and with different historical periods. The protective presentational boundary can be an adobe wall in New Mexico or Khartoum; it can be a picket fence and garden and verandah in ante bellum Charleston; and it can be a magnificent religious or civic façade (either with or without entry courts, gates and gardens). In all cases, on one side of the boundary is public environment – where anonymous people come and go - and on the other side of the boundary is a domain which is controlled.

Those on both sides of the boundary understand the system. When we are in public areas we know where we belong, as do those who are in the more controlled – or private – realm. (In this sense, civic and religious buildings would qualify as the controlled/private realm.) With this clear and universally understood system of physical relationships and signals we gain an immense benefit – whichever side of the boundary we are in: Because the model is clear and legible, we move easily within it. We understand the protocol – almost subconsciously – and we are psychologically comfortable.

If we are in the controlled/private realm, we do not feel threatened by those who do what people do in public because they are where we all understand they are supposed to be. If we are in the public realm we understand where we are entitled to be, and we can move and act comfortably. The act of penetrating the protective presentational boundary (to enter either the private realm or the public realm!) is a comprehensible part of our social lives. And in a traditional urban environment the signals and spatial relationships are all in legible, comprehensible place.

Not many of us, of course, live in single-street villages, and it is interesting where the model we are exploring leads as we rise in complexity, density and size of urban form.

the system convolutes:

Topology is a discrete – and rather arcane – field of high-level mathematics (and geometry) which deals with relationship rather than with visible dimension and form. This paper is by no means high-level mathematics – but it is a study of relationship rather than form, and therefore it is a topological analysis. (The discovery and proof that the Moebus strip is a 3-D object with only one side is topology – and all Moebus strips are topologically the same – no matter how large, of what colour, or what material.)

The reason for this aside is to remind that this is a review of relationship – not style nor historic period – and, more importantly, to lead us to the next step:

Thus far we have explored some basic relationships. The guiding proposition of this essay is that with these basic relationships the entire fabric of the historical city was made. The intertwining of these relationships is endemic to all pre-twentieth century towns, villages and cities. And the root source of these relationships is the clarification of territorial position – the relation between where “I” and “my” are entitled to be, and where “they” and “their” are entitled to be.

The next step in complexity is a 1-1/2-street village – a village with a “T” intersection. Here the protective presentational boundary follows the streets and continues to create the continuous boundary between public and private realm.

And, again, the next step in complexity (in either a single or “T” street village) is a distortion in which streets are no longer simply streets – or, to clarify, when the space between opposing faces of the protective presentational boundary is expanded, and the boundary is able to “make” special more-than-a-street streets – or public places.

And this public domain exists not only as routes for movement, but as parks and markets – the open space of the city:

Up to this point in this investigation the geometry of relationships is pretty straightforward, and the key insight has more to do with understanding the territory-clarifying function than with demonstrating complex geometric patterns.

The next step in this progression is really the core “leap” of this discussion – and the one which leads to some interesting discoveries about how cities really fit together.

When villages reach a scale where they cannot simply stretch ad infinitum as single street, nor T-street, nor multi-branched streets – they have to achieve another generation of geometry.

This next generation of geometry is the logical next step. If private/controlled space is to meet public space through the filter of the protective presentational boundary, and if there are getting to be too many private territories to stretch forever on a few streets, a network of streets and paths has to be created, and private space has to fold in on itself to create “islands” of territory surrounded by protective-presentational-boundary:

intersections of streets

from branching of streets to a network of streets

a network of streets, lined with protective presentaional boundaries

And once those islands become the tools (or the modules) of city building, expanding the scale of cities becomes a piece of cake. Each of these islands is surrounded by its set of private/protective presentational boundaries. Many islands together surround and define the streets and plaza of historic cities, and it is this symbiotic relationship which is the basic building block of larger urban agglomerations.

The protective-presentational boundary is intermediary between the public network and the private domains:

The pattern which emerges is of course familiar. It is a pattern of city blocks. And the city block, seen in this way, can be defined as a private domain, or set of private domains, surrounded by a protective-presentational boundary and bounded in turn by the public network.

This definition does not limit the city block to endlessly repeated rectangular pieces of property, nor does it dismiss the block as a convenient means of sub-dividing property. Instead it allows us to see the city block as an essentially territorial model for city-building, whose shape can vary almost infinitely, as those blocks in Lima demonstrate:

(Note in particular the large, extremely complex, block indicated with cross-hatching.) The protective-presentational boundary, in all of its meanderings, remains a consistent intermediary between the public and private domains.

variable character in a consistent model:

Once this model of territory-defining city blocks with a continuous edge of protective presentational boundary becomes the lens for looking at pre-twentieth century cities, the consistency of the model is astounding. As bold as it may sound, there are no exceptions to the model in pre-twentieth century non-tribal permanent settlements.

A city block is often thought of as a rectilinear tool for selling and developing land. In fact, it can have a wide range of shapes and spatial/geometric intricacy; the determining relationship (remember topology!) is what we have discussed: a block is defined as a continuous protective presentational boundary around the perimeter of a collection of private/controlled environments – which, in turn, define and create the public realm.

Depending on the reader’s cultural heritage, the preceding discussion will bring to mind some quite different normative models of what this city block is. Key variables include geometry, scale, density, the existence of open space within the block, the number of individual properties in a block, the intricacy and “open-ness” of the exterior face of the block, and the physical depth of the protective presentational boundary.

• The perimeter of a block can be a relatively simple form – or it can meander to a tremendous extent. The apparent contortions of the outline of some vernacular blocks have a strong resemblance to illustrations of fractal geometry! If we look closely at examples of these “fractal” blocks, we find that the consistency of the protective presentational boundary as filter/intermediary element remains intact, and we find that private domain always and only exists on the “protected” side of the protective presentational boundary.

• Blocks vary in scale from tiny and intricate to collections of properties of 200 meters or more in length.

• Densities of blocks, as well, can vary over a wide range – from single family houses in farming villages (or in modern suburbs) – to the densely-packed patterns of Paris, Barcelona, Tokyo and Manhattan.

• Most city blocks contain more than one property, and more than one protective presentational boundary filtering between public anonymity and private/controlled turf. However, there are many historic examples of single-entity blocks with continuous protective presentational boundary around their entire perimeter. The most obvious of these are cultural, religious or institutional entities – temples, government buildings, university buildings, etc. In terms of our development model, the important distinction is that such single-owner-controlled domains really do have a protective and presentational boundary around all sides – and do not expose an un-protected nor un-presentational, nor non-bounding boundary anywhere along their perimeter.

• This idea that traditional blocks do not leave “an exposed underbelly” anywhere around their perimeter is a key – perhaps the key – conceptual lens with which to examine historic urban fabric. And explicitly pointing out this concept leads to two important asides:

• The first of these is that as I think of this model, and observe its consistency, I have a recurring analogy:

Adult Musk Oxen famously face outward in a circle and herd their young and frail to the centre of the circle when being attacked by wolves. Though the anonymous public is not analogous to threatening wolves, there are real similarities, and it is architecturally interesting to equate a bunch of shaggy manes, huge horns and snorting nostrils to an architectural version of the protective presentational boundary!

• The second is a reminder that the continuous protective presentational boundary does not have to be water-tight nor menacing. Spaces between buildings and friendly gestures are easily compatible with the urban function of the boundary: Its main urban duty is to make legible the edge between public and private.

behind the boundary

The private domain which constitutes the city block varies considerably. It can be the domain of an individual family, or a number of families; or it can be the domain of institutions or businesses. Institutions such as government or church are more public than are families. However, in relation to the real public domain of streets and open space they are relatively private: One who enters recognizes restrictions which do not apply to movement in the public network. These increased restrictions are supported by tradition and sanction, and often by physical barriers and schedules.

Churches, law courts, corporate headquarters, office buildings, or museums are all buildings of quasi-public character. They are open to the average citizen, but they are the domain of a set of initiates: of insiders. They are entered only under certain circumstances, and on entering one recognizes his move from the public network into a private domain. And this private domain requires a certain etiquette different from the etiquette of the public network.

These public buildings which are private domain sit in the urban fabric just as the more private domain of housing. They often have more elaborate facades, or in our developing language, their protective-presentational boundaries are more powerful (more inviting, more forbidding, more grand, more decorative, or even more austere). And they often constitute an entire city block. However, these are not differences in structural relation to the city: The protective-presentational boundary is still the intermediary between the public network and the private domain. Whether public buildings make up all or only part of a city block, a continuous protective-presentational boundary exists between private domain and public network.

private open space

The private domain does not consist only of buildings. It is made up, too, in greater or lesser degree, of open space.

There are two kinds of private open space. This may be understood if we look at a typical row-house with its front and back yards:

The front yard is in fact not so much private open space as it is a constituent element of the protective-presentational boundary: fences, gates, flower gardens, hedges, and well- (or ill-) kept lawns work in tandem with the shutters, portico, and front steps of the facade to make up a rather elaborate protective-presentational boundary. All exist to establish the relationship of the private domain with the public.

The back yard, on the other hand, is what we should properly call private open space. It has three characteristics which are common to all private open space in the urban environment: 1) it is relatively more private than the public network, 2) the protective-presentational boundary exists between it and the public network, and 3) it is separated from the building it serves by something less than a protective-presentational boundary (in the row-house we can compare the facade with the typical backside, with its un-decorated windows and minimal service door).

Private open space is not always behind the building; it can also be in the centre of a private domain, as in the typical court-house of early Greece or Pompeii:

Or it can be at the front of the private domain as in some Greek and Mexican villages:

This is not a very common model, and it makes unusual demands on the protective-presentational boundary. * The more common solution to this condition can be seen in British nineteenth century industrial “back-to-back” housing, which retains a front yard as a protective-presentational boundary but dispenses altogether with true private open space:

And with surprising frequency the private domain is made up only of building - with no privately-owned open space at all. Residential examples can be found in most of old Amsterdam and in a number of Italian villages.

Private open space can be behind, in the middle, or in front of the building - or it can be non-existent. These diagrams show private open space as an element in low or medium density housing. There is a parallel development of private open space in higher density housing and for non-residential buildings. The main difference is that the greater the number of people who use a private open space, the stronger must be the boundary between private open space and its attendant building.* For example, in the Greek single-family courtyard house the boundary between the courtyard and the rooms around it is not very important for territorial definition. In fact it is often no more than a colonnade separating the rooms from the courtyard; the courtyard serves as both garden and circulation space for the house. In Seville, on the other hand, there are apartment houses with large garden-courtyards. These courtyards are used by a larger number of people than are those of the Greek single-family house. The higher density use demands a stronger wall separating the building from its private open space. This stronger separation remains a boundary within the private domain, and is not equivalent to the protective-presentational boundary between public and private.

kinds of city blocks

The preceding diagrams show how private open space exists for individual buildings. We can transfer these diagrams to plans of city blocks. When we do, five basic city block patterns emerge:

The first is the city block with no private open space. As mentioned above, this pattern is surprisingly common. It is especially common for non-residential buildings. In some cases the entire city block has extensive private open space which is the domain of a single family group (2), as in the Palazzo Farnese in Rome. A related pattern is that with a number of enclosed courts (3). Examples of Greek courtyard houses and Seville apartments have already been mentioned.

Two city block patterns which have less explicitly private open space are the sub-division with “backyards” facing each other (4), and blocks with a service lane (5). The first of these patterns is common in London, Boston, and many contemporary low and medium-density housing developments.

The service lane pattern was built as early as the fifth century B.C. in the Greek colonial town of Olynthus, and has been common in the nineteenth and twentieth centuries for both low and high density building. In spite of their more public, contiguous private open spaces, these two patterns reserve relatively greater privacy and control to the block centre. The protective-presentational boundary of the block faces the street and there is generally some signalling that entry into the block centre is an intrusion into the domain of others.

These five block types encompass a large number of actual city blocks, each with its own peculiarities. Once again, in spite of variation in detail all of these city blocks are the same in that they consist of a private domain or group of private domains surrounded by a protective-presentational boundary which is in turn bounded by the public network.

carving

City blocks, like everything else in the city, are not static. Often small commerce “booms” in a neighbourhood. Existing street frontage is quickly exhausted and ambitious entrepreneurs search for new frontage in the area. They know that their development must be contiguous with the popular area; if they open a store the next street over they will fail to benefit from the boom. So instead of going to the next street they make a new street. This is done by cutting into the existing protective-presentational boundary of storefronts with mews or by developing the private open space of the block as new public network:

The most interesting fact in light of our notions of public and private domain is this: The expansion of the public network is accompanied by an extension of the protective-presentational boundary; the boundary, in the form of new facades, signage, and shop windows remains the continuous intermediary between the public network and the private domain.

This extension of commercial frontage into the private domain is in effect a carving-out of the private domain by the public. This carving-out is not limited to piece-meal commercial expansion; it is common on a grand scale in Paris and London - in fact in most European capitals. Baron Von Haussman’s carving in Paris is probably the most well-known, and certainly the grandest, single example. Such carving typically involves the creation of parks, grand squares, or entrance plazas for public buildings. But residential examples also exist; Place des Vosges in Paris is a particularly clear example:

The protective-presentational boundary is a constant intermediary between the new element in the public network and the private domain. It is interesting that Von Haussman engaged architects to do the facades which lined his boulevards but left the actual building design to developers. (An insult to present-day architects, but a reflection of contemporary Beaux-Arts training - and a reflection of the traditional importance of the protective-presentational boundary.)

pastoral backdrop

One normally thinks of the public open space of cities as parks and streets. However, there is a third kind of open space which is not park, yet which is often confused with park. Before discussing parks and how they fit into the urban fabric we will examine this third kind of urban space - and avoid some possible confusion.

Many villages consist of a main street or an intersection of two streets. These villages, though small, are essentially urban, and exhibit the characteristics I have been discussing.

Private domain generally consists of houses with courtyards and out-buildings behind. Behind these there is open space. This open space is usually farmland or forest. It may be divided into privately-owned parcels or it may be communal. In either case this space is not urban; it is of the countryside and not of the city; it is not traversed regularly as street or square, and use by extended groups occurs with planting, harvesting, or hunting - occasions of the countryside and not of the city. This surrounding open space is the pastoral backdrop of the community. Its main characteristic, besides being bucolic, is that it is not part of the public network; it is not part of the lines of movement within the city.

In many Greek and medieval fortified towns the walls are some distance from the town itself.

In such towns the pastoral backdrop exists in much the same way as for the un-fortified village. The only exception is that the surrounding wall forms part of the view and occasional soldiers might use the path on the outskirts. The public network remains firmly in the middle.

The pastoral backdrop can be contiguous with the private domain with no intermediate protective-presentational boundary. Backyards abut this open space directly with no apparent loss of territorial clarity. The pastoral backdrop, because it is not traversed by the public in its normal movements, creates no infringements on the private domain. And there is no necessity for the private domain to protect itself from nor present itself to the pastoral backdrop.

In the single street village the pastoral backdrop recedes “to infinity”. The outskirts of larger cities are sometimes endless agricultural hinterland, too. But in any growing metropolis such edges are soon replaced by new city. Pastoral backdrop also exists within the city and it retains the same structural characteristics: 1) it is not part of the public network, 2) it is bucolic, and 3) it can abut private domain with no intermediate protective-presentational boundary. The pastoral backdrop as agricultural hinterland retains these characteristics almost by accident. It remains untraversed simply because no one is there to traverse it, and it does not infringe on private domain because only countryside is there to confront private domain. Within the city the pastoral backdrop has people passing by and in order to remain untraversed it must be impenetrable. In order that it not infringe on private domain it must act as a buffer between private domain and the rest of the city.

Extensive dimension alone is not sufficient to provide this impenetrable buffer. A typical pastoral backdrop within the city is an area of dense planting. It can be a buffer between two areas of private open space:

Or it can protect private open space from a portion of the public network - such as a park:

Pastoral backdrop does not necessarily abut private open space, and can exist as a buffer entirely within the public network, for example as an element insulating portions of a public park from each other:

Impenetrability can also result from difficult terrain:

Or from intermediate bodies of water (rivers or ponds):

The pastoral backdrop as agricultural hinterland is an expanding vista rather than the closing edge of a dense wood:

hill and dale as vista vs.:

edge as the important experience.
increased dimension may increase the efficacy of the buffer, but it does not alter the primacy of the edge in determining one’s experience.

We experience bodies of water, too, as expanding vista. They are not susceptible to new urban growth, and are impenetrable. They are diagrammatically similar to agricultural hinterland and have the added advantage of (relative) immutability.

Bodies of water can directly abut private open space:

Or they can be bounded entirely by public network, as in most beach towns:

The private residence whose backyard is bounded by a steep bluff which meets a public beach is a nice example of all of these urban elements comfortably together:

To re-iterate: The pastoral backdrop is experienced from the outside. One passes by it, and it is its edge which determines one’s experience.

The primary function of the pastoral backdrop within the city is that of bucolic buffer:

And the main characteristic of the urban pastoral backdrop is its impenetrability.

A dense wood has the advantages of being Nature, changing with the seasons, having its own life, sounds, and scents. But its structural relation to the city is limited to its edge. If the pastoral backdrop were a mural of nature with cotton candy fluff behind, it would have exactly the same relation to the city.

The pastoral backdrop is a bucolic, impenetrable view. An extended vista is the same as the edge of the wood.

Urbanists customarily make no distinction between pastoral backdrop and urban park and refer to both simply as “parks”. Though both are elements of relief, their structural functions are quite different. One can pass through parks; while one lives or passes by pastoral backdrop. On one hand this is an aesthetic distinction between two modes of experience, it is also a structural distinction between two urban elements. Pastoral backdrop has a number of uses and attributes, but its specific territorial-structural importance is that it is land which can abut private domain directly with no intermediary protective-presentational boundary.

Woods with occasional paths and lakes with occasional sailboats are still pastoral backdrop. They are passable to a limited extent, but not passable for normal urban movement. The pastoral backdrop is an edge or view which is normally experienced from the outside, which is not part of normal urban movement, and which creates no infringement on surrounding territory. When, as a result of changing circumstances, there is no buffer of distance or impassable terrain between a used portion of the pastoral backdrop and its edge, the pastoral backdrop of course ceases to be pastoral backdrop - and becomes park.

parks

The public network includes not only the movement channels of the city but its amenity spaces - its parks, be they streets, sidewalks, market squares, plazas, playgrounds, “vest pocket” parks, or large city parks. Though often bucolic, the urban park differs from pastoral backdrop in that it is part of the public network and very much part of the city.

The public network, as streets and parks, is bounded and “held at bay” by the protective-presentational boundary of surrounding private domain. Urban parks, perhaps best defined as expansions in the public network, have always reflected this characteristic of being held at bay. The paradigmatic example is the market or fountain square of small European villages:

Here we can see clearly the square as an element of the public network surrounded by facades. There are seven other ways which parks can sit in cities. They are different in detail, but all are characterized by being 1) part of the public network, and 2) held at bay from private domain by a surrounding protective-presentational boundary. Because of this consistency, we can say that all urban parks are topologically the same in their relationship to the urban fabric.

Many large cities grew with extensive areas with no parks at all. The street was not only a route, but the focus of social life - the realm of work, relaxation, and play. Though most cities have public parks, the street itself is often the most-used “park” in the urban environment.

Parks often appear to be separate domains within a city block. This may result from piecemeal building demolition, and vacant lots being made into parks, or from more deliberate planning. The result may be an apparent hole cut out of the block, as in the “vest pocket” park.

Or the result may be more formal:

The most common image of the city park is that of a piece of land surrounded by streets and called a park:

A similar pattern is the park partially bounded by a pastoral backdrop (for instance the beach and promenade of many oceanside cities):

Public and quasi-public buildings, such as government buildings, churches, or museums, often sit within extensive open grounds:

In addition to entry facades they preserve a protective-presentational boundary as they face the surrounding public domain of park. Two examples which may help illustrate this are the Metropolitan Museum in New York’s Central Park - especially with its park-side facade - and Notre Dame in Paris. Notre Dame is particularly intriguing because it is so present within its surrounding open space that it creates three separate and quite distinct parks: a front plaza, a band of seating and trees to the south, and a large open park at the rear of the church (whose apsial flying buttresses are so magnificent that one hardly feels cheated by being at the “rear”.)

A final category of urban park is not always distinguishable from the last. It is the park which includes buildings truly part of the public network - in that one enters the building with the same ease as one enters the park itself.

The Parthenon and other buildings of the Athenian acropolis have this character. As did (presumably) Greek and Roman fora.* Park pavilions are a more contemporary example: these may be picnic shelters, plant conservatories, or the monkey house at the zoo. The line is not really clear, and depends to some extent on one’s perception of public and private. It is tempting to include such universally familiar and enter-able churches as Notre Dame in Paris as an example of the pavilion in the park - while excluding churches which do not have this quality of universal accessibility. Using Notre Dame as an example of both of these categories high-lights the fuzzy edge separating them. However, the distinction should be clear when we compare the extremes of the large formal museum, which is distinctly not a pavilion, and the picnic shelter. Within our evolving understanding of urban form, the notable distinction of the pavilion in the park is that it does not require a protective-presentational boundary between itself and the surrounding public network. In fact, the less distinct the protective aspect of the building edge the more likely is it to be a pavilion - and just another part of the park.

These are the eight ways of setting parks in the city. All are no more than variations on the first, and all reflect the park as an expansion in the public network which is held from neighbouring private domain by its protective-presentational boundary. The diagrams are simplified and suggest a certain scale and form. One should keep in mind that examples of each park type also exist which are complex in form and grand in scale.

conclusion

I have been examining these ideas of urban structuring in some detail. Though the detail adds up, the central concept is simple: The system of city blocks and city parks, a system with which we are all familiar, is an effective territorial model for urban building. I have tried to keep jargon to a minimum, and the only new phrases which seem inevitable are “protective-presentational boundary” (because “facade” is not broad enough to recall its three-dimensional possibilities), and “pastoral backdrop” (because it is important to distinguish between urban parks and bucolic edges - both of which are usually referred to as “parks”).

The traditional pattern of city-building gives territorial clarity to the urban environment. This clarity is as much a boon to strangers passing through as to residents. The stranger has little difficulty deciphering the signals which the environment presents. He knows where he may go and where his going might be unwelcome or regarded as intrusion. Residents can feel more comfortable about the presence of outsiders because there is no confusion about where those outsiders belong. Residents, too, have a certain amount of confidence about their right to colonize their own territory because its limits are so easily perceived.

The security which traditional patterns provide has an interesting side-effect: The resident who has little confusion about the relation of his private domain to the public domain and neighbouring private domain can accept greater variety in his surrounding environment. Clear territorial patterning will not stop racism, class consciousness, nor a distrust of different kinds of land use. But without clear territorial patterning it is almost impossible to deal with any but the most homogeneous neighbouring activity. The traditional structure of cities permits flux and emergent ecumenicism - and in environments which lack a legible territorial framework evolutionary acceptance of heterogeneity is very difficult.

In cities, economic and social patterns are constantly changing. An environment which cannot accept such demographic flux would be a poor framework for the long-term survival of any urban agglomeration. The particular strength of traditional urban structure is that it provides an ideal framework for this flux. An activity or group will be attracted by existing patterns in an area. As it begins to insert itself into a neighbourhood, it takes over an identifiable piece of private domain - or slot in the city block. Similar or complementary uses are in turn attracted and fill nearby slots - in the long term transforming the character of the area. The advantage of the city block is that it can accept this gradual insertion, interaction, and expansion (or even disappearance) of diverse activities without at any point disturbing the equilibrium nor territorial clarity of the area.

(There are limits of course; a striptease joint in a middle-class residential neighbourhood is the kind of extreme which would bring other forces into play, whereas a dentist’s office would cause little reaction. Again, the point is not that city blocks guarantee completely open-ended welcome to any and all; traditional territorial patterning, though, provides a framework which permits the natural, anarchic, flux of urban activity. )

The pattern of city block - public network - pastoral backdrop is the inevitable result of coping with a set of urban realities: the juxtaposition of public and private domains, each with its qualitative and functional requirements; the nature of urban growth; and a need for territorial clarity. The structure implicit in this pattern is simple and direct, and can provide a handy conceptual tool, or model, for the design of cities. Rather than a limiting model, it has proven over the centuries to be liberating - permitting a full range of spatial and architectural quality, and proving as applicable to a tiny hill village as to high density massive urban agglomerations.