Here's a post that gives a nice overview of the project.
Here's the New York Times review of the original show of these peices at the Guggenheim, which includes this fun, Calvino-esque passage:
It's clear... that the city's inhabitants are segregated into day people, wholesome types who study at home with their children by means of electronic devices, and night people. "Tattered ghosts in phosphorescent clothing," the night people sound a lot like the more Felliniesque denizens of the Lower East Side, being given to masks and elaborate makeup; they "mutter a lot" and "often carry around personal abstract structures" that they exchange "according to mysterious rituals." And while they have homes in the Over-building, they frequently sleep in the cubby holes of the Under-building, ignored by day people going about their business.And here's a post with lots more images to look at.
via Boing Boing