This building in Montpellier (France) that Zaha Hadid designed, contains three institutions: sports, archives and library. The deisn is based on a tree-like structure, encompassing the typical qualities of the three parts: the solid archives are at the bottom, on this the more open libarry is placed, and on top are the sports, where the building is much lighter. The three parts share a whole bunch of functions in the heart of the building.
So the underlying scheme is actually quite simple, but the building looks anything but unspectacular: the projecting volums mark each of the individual entrances, and follow the tree-like basic scheme.
More information on this project can be found here.