The Space Needle is 184 meters tall. Despite its height, the center of gravity is only 1.5 meters about the ground.
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.
See also: Seattle’s World Fair 1962 picture postcard0