Extraordinary technological advances have taken tall buildings to new heights, quite literally. Whereas in 1973 Chicago’s Willis Tower was the tallest of them all at 442 meters (1,451 feet), Jeddah Tower in Saudi Arabia will assume that distinction in 2020 or thereabouts, leapfrogging all other super- and megatall buildings with a height of 1,000 meters. Advances in structural systems, high-strength concrete and steel, vertical transportation, and glass and steel façades largely made it possible.