This text from The City & the City by China Mieville was circulated as a metaphor for the symposium:
The twin cities are composed of crosshatched, alter, and total areas. “Total” areas are entirely in one city, the city in which the observer currently resides. “Alter” areas are completely in the other city, and so must be completely avoided and ignored. Between these are areas of “crosshatch”. These might be streets, parks or squares where denizens of both cities walk alongside one another, albeit “unseen.” Areas that exist in both cities usually go under different names in each one. There is also Copula Hall, “one of the very few” buildings which exists in both cities under the same name. Rather than being cross-hatched, it essentially functions as a border. It is the only way in which one can legally and officially pass from one city to another. Passing through the border passage takes travellers, geographically (or “grosstopically”), to the exact place they started from – only in a different city.