Glasgow School of Art -- Charles Rennie Mackintosh
Charles Rennie Mackintosh's Glasgow School of Art of (designed 1906-7; completed 1909) was one of the twentieth Century's first true architectural masterpieces. Mackintosh designed it at the age of just twenty-eight.
That's a model (above) of the completed building, the Library (below, left and right) and the West facade (left)
A film showing some of Mackintosh's work is available at this site. And a 3d 'tour' of Mackintosh's beautiful light-filled Hill House Drawing Room is available at this site. It's amazing what you find on the old Interweb when you decide to really look.