Palais de Tokyo, designed for the International Exhibition of 1937 by Dondel, Aubert, Viard and Dastugue (who won, controversially, in an open competition against proposals by Robert Mallet-Stevens and Le Corbusier). The interior has been redesigned a number of times since then. The building was vacant from 1976 (when the modern art collection was moved to the Pompidou Centre) until relatively recently. It's now the ridiculously cool home of cutting edge contemporary art. Love.