Dome

Context view, looking south from Queen Anne Hill, with Mt Rainier in the distance at right; Built for the 1962 World's Fair. At approximately 605 feet (184 m), the Space Needle was the tallest building west of the Mississippi River at the time it was built by Howard S. Wright Construction Co., but is now dwarfed by other structures along the Seattle skyline, among them the Columbia Center, at 967 feet (302 m). The earthquake stability of the Space Needle was ensured when a hole was dug 30 feet (10 m) deep and 120 feet (40 m) across. An army of cement trucks (467 in all) took one full day to fill it up. In fact, the foundation alone weighs almost 6,000 tons and there are 250 tons of reinforcing steel in the base. With this concrete base weighing the same as the above-ground structure, the Needle's center of gravity is just 5 feet (1.5 m) above ground level. The entire structure is bolted to the foundation with 72 bolts, each bolt being 30 feet (10 m) long. Source: Wikipedia; http://en.wikipedia.org/wiki/Main_Page (accessed 2/8/2008)