Willis Tower ( former Sears Tower) (bounded by Wacker Drive, Jackson Boulevard, Franklin Boulevard and Adams Street) is one of the world’s tallest buildings, topping off at 1,450 feet. Designed by Skidmore, Owings and Merrill and opened in 1974, Willis Tower consists of black aluminum and bronze-tinted glass on a structural steel frame, and it encompasses 101 acres of floor space.
The skydeck, which was renovated in 2000, offers a multi-media presentation and spectacular view of Chicago and beyond. Chicago's second highest building is the 80-story AON Center, formerly the Amoco Building (200 E. Randolph Street), which also opened in 1974. Designed by Edward D. Stone with Perkins and Will, the slender building stands out on the skyline and dwarfs its neighbor, the Prudential Building.
The John Hancock Center (875 N. Michigan Avenue), another Skidmore, Owings and Merrill project, opened in 1969 and is distinguished by the steel cross-braces which make huge X's on each side. Three states, Illinois, Indiana and Wisconsin, are visible from the observatory on the 94th floor.