(YouTube link)
Christian Schallert has a 258 square foot apartment in Barcelona. With some imagination and design help, he remodeled it into a transformable space. Everything is stored away. He opens doors to use the kitchen, and moves things around to have a dining area or bedroom. Link -via Buzzfeed
http://www.neatorama.com/2010/04/29/24-room-transformer-apartment/
More than once, actually.
http://www.neatorama.com/2009/01/28/one-344-sq-foot-room-with-24-possible-layouts/
Are those slums?