La Geode is a fascinating structure in Paris' Cite des Sciences. It's a 36 meter diameter IMAX movie theater built in 1985 and has the only 12.1 surround sound system in the world (can't say I noticed). More impressive are the ~6,500 triangles that coat the sphere: they are placed in groups of 4 with a tolerance of within 1/10 millimeter. No triangles actually touch each other to allow for expansion due to temperature variations. Best of all? The reflections!