Some extracts from Foucault's writing on a particular spatial concept that he identified as heterotopias:
... One could say, by way of retracing this history of space very roughly, that in the Middle Ages there was a hierarchic ensemble of places: sacred places and profane places: protected places and open, exposed places: urban places and rural places .... It was this complete hierarchy, this opposition, this intersection of places that constituted what could very roughly be called medieval space: the space of emplacement.
... This space of emplacement was opened up by Galileo ... in his constitution of an infinite, and infinitely open space. In such a space the place of the Middle Ages turned out to be dissolved. as it were... starting with Galileo and the seventeenth century, extension was substituted for localization.
... Today the site has been substituted for extension which itself had replaced emplacement. ... Our epoch is one in which space takes for us the form of relations among sites. ... And perhaps our life is still governed by a certain number of oppositions ... that we regard as simple givens: for example between private space and public space, between family space and social space, between cultural space and useful space, between the space of leisure and that of work. All these are still nurtured by the hidden presence of the sacred.
...we live inside a set of relations that delineates sites which are irreducible to one another and absolutely not superimposable on one another.
Of course one might attempt to describe these different sites by looking for the set of relations by which a given site can be defined. For example, describing the set of relations that define the sites of transportation, streets, trains ... the sites of temporary relaxation -cafes, cinemas, beaches. ... the closed or semi-closed sites of rest - the house, the bedroom, the bed, el cetera. But among all these sites, I am interested in certain ones that have the curious property of being in relation with all the other sites, but in such a way as to suspect, neutralize, or invent the set of relations that they happen to designate, mirror, or reflect. These spaces, as it were, which are linked with all the others, which however contradict all the other sites, are of two main types.
First there are the utopias. Utopias are sites with no real place...(they) are fundamentally unreal spaces.
There are also, probably in every culture, in every civilization, real places - places that do exist and that are formed in the very founding of society - which are something like counter-sites, a kind of effectively enacted utopia in which the real sites, all the other real sites that can be found within the culture, are simultaneously represented, contested, and inverted. Places of this kind are outside of all places, even though it may be possible to indicate their location in reality. Because these places are absolutely different from all the sites that they reflect and speak about, I shall call them, by way of contrast to utopias, heterotopias.
Its first principle is that there is probably not a single culture in the world that fails to constitute heterotopias...(which) obviously take quite varied forms ... (but we can) class them in two main categories. In the so-called primitive societies... crisis heterotopias, i.e., there are privileged or sacred or forbidden places, reserved for individuals who are, in relation to society and to the human environment in which they live, in a state of crisis: adolescents, menstruating women, pregnant women. the elderly, etc...today (these) are being replaced, I believe, by what we might call heterotopias of deviation: those in which individuals whose behavior is deviant in relation to the required mean or norm are placed.
The second principle of this description of heterotopias is that a society, as its history unfolds, can make an existing heterotopia function in a very different fashion.
Third principle. The heterotopia is capable of juxtaposing in a single real place several spaces, several sites that are in themselves incompatible.
Fourth principle. Heterotopias are most often linked to slices in time - which is to say that they open onto what might be termed, for the sake of symmetry, heterochronies. The heterotopia begins to function at full capacity when men arrive at a sort of absolute break with their traditional time.
First of all, there are heterotopias of indefinitely accumulating time, for example museums and libraries...
Opposite these heterotopias that are linked to the accumulation of time, there are those linked, on the contrary, to time in its most flowing, transitory, precarious aspect, to time in the mode of the festival. These heterotopias are not oriented toward the eternal, they are rather absolutely temporal [chroniques].
Fifth principle. Heterotopias always presuppose a system of opening and closing that both isolates them and makes them penetrable. In general, the heterotopic site is not freely accessible like a public place. Either the entry is compulsory, as in the case of entering a barracks or a prison, or else the individual has to submit to rites and purifications
Sixth principle. The last trait of heterotopias is that they have a function in relation to all the space that remains. This function unfolds between two extreme poles. Either their role is to create a space of illusion that exposes every real space, all the sites inside of which human life is partitioned, as still more illusory (perhaps that is the role that was played by those famous brothels of which we are now deprived). Or else, on the contrary, their role is to create a space that is other, another real space, as perfect, as meticulous, as well arranged as ours is messy, ill constructed, and jumbled.
Read more, dossier heterotopia: http://www.foucault.info/documents/heteroTopia/