Boundaries structure and order lived urban space. They not only separate and control different areas, but with their material appearance they also make the delimited space with its specifics perceivable as an entity at its own right. Georg Simmel already emphasised the dependence of boundaries on social configurations and processes[1]. Materially marked boundaries thus reflect symbolic or social boundaries[2] and manifest them spatially. Accordingly, boundaries, like the entire urban space, are socially produced[3]. With Martina Löw and Gunter Weidenhaus, boundaries and boundary zones can even be described as social spaces themselves[4] – and their analysis promises far-reaching insights into the social structuring of the city[5].

With regard to spatial/material boundaries of cities, intensive research has been conducted on the delimitation of the city from the surrounding countryside (city walls, pomerium)[6] as well as – within the city – on the boundary between private space and public space (namely building entrances and façades)[7]. In the proposed session, we will choose a different angle of looking at boundaries: We want discuss boundaries that structure and divide the inner city space, and more specifically open public squares (agorai/fora)[8].

The special focus will be on material boundaries that have been intentionally designed – such as architectural buildings (e.g. colonnades, inner-city gates), boundary stones, fences, grids, shear walls, but also intentionally created watercourses/water areas or tree plantings. If possible, such (often ephemeral) boundaries should be addressed from a diachronic perspective in order to show how social interests are reflected in the ordering of public space.

Five aspects will be mainly considered during the session:

- Material strategies of boundary making and marking. The boundaries‘ materiality and design have a direct impact on the aesthetic, semantic and thus also social quality not only of the boundary but also of the adjacent areas. We would like to ask about the aesthetic qualities and (social) meanings of different forms of boundary making.

- Performativity of boundary interactions. The crossing of boundaries often takes on a performative character and is ordered by ritual norms ('rites de passages'). We are interested in how such performances relate to the materially designed space.

- Degrees and modes of (physical and social) permeability. The permeability of borders can be designed very differently. Entrances and transition zones in particular play a central role in regulating social interaction.

- Temporality: ephemerality versus permanence. A basic characteristic of boundaries is its temporality. Any architectural arrangement, boundary markers included, can be changed and transformed over time. This is particularly obvious when ephemeral materials or ephemeral arrangements are used for boundary markings. But even stable boundaries like gates can be used variably over time depending on certain forms of use: They can represent a boundary at one moment and a permeable passage situation at another.

- Boundaries as a result of (social) negotiation processes. , Boundaries are not only socially designed, they require an authority to enforce them and a general acceptance by at least a part of the different actors. Therefore every boundary can be described as the result of negotiation processes, which are directly linked to concurring power constellations and interests.