...it can be said that each dwelling unit is realized by experience of two rooms and the city when passing along outside stairs. When you go up outside stairs, you will have experience that it is a wonder climbing a big mountain such as a city. It seems that you have your own house in the foot and summit of a mountain, respectively.

By Sou Fujimoto Architects (can't remember where I came by this link). It says the project was supposed to have been completed in 2008. I would certainly like to see the real thing.