Which notable building was designed by Helmut Jahn in Chicago?

Helmut Jahn is known for his innovative and modern architectural designs, and one of his most significant contributions to Chicago's skyline is the State of Illinois Building. Completed in 1999, this building features a distinctive modernist style with a glass facade and a dramatic cantilevered overhang, showcasing Jahn's unique approach to blending functionality with aesthetics. His use of reflective glass and sharp geometries in the design of the State of Illinois Building creates a striking visual impact and integrates well with the surrounding urban environment.

In contrast, the other buildings listed have different architects associated with them. The Willis Tower, formerly known as the Sears Tower, was designed by Skidmore, Owings & Merrill; the John Hancock Center was designed by Bruce Graham and Fazlur Rahman Khan; and Water Tower Place was designed by Edward Dart. Each of these buildings has its own architectural significance, but they are not attributed to Helmut Jahn. His work on the State of Illinois Building is a testament to his influence on modern architecture in Chicago.