Very tall buildings are a tough sell in Paris. The Parisians don't want their lovely low-rise city looking too much like Houston. So Swiss architects Jacques Herzog and Pierre de Meuron knew they'd have to win over skeptical neighbors to get their 50-story tower built. Le Project Triangle, a combination office/hotel, is the first skyscraper to be approved since Paris lifted a 31-year-old ban on high-rise construction in the city center. Using computer modeling, the designers of Beijing's "bird's nest" Olympic stadium came up with a building almost as startling: a slender glass-and-steel triangle, like a shark fin, that they say won't cast shadows on surrounding streets. The pyramid is one of history's oldest building shapes, but a slim triangle? That's new. Is it the shape of things to come?