The Sunsphere, the iconic theme structure of the 1982 World's Fair, was built to honor the exposition's energy theme as an homage to the original source of all energy on earth. It was designed by Community Tectonics, led by architect Hubert Bebb (1903-1984), who was originally from Illinois, worked as a designer at the 1933 Chicago World's Fair, and made his career in and around the Smoky Mountains. Bebb is especially known for the modernist Observation Tower at Clingman's Dome (1959). In 1982, the Sunsphere was touted as the most perfectly spherical building in the world. The sphere is 74 feet in diameter, and its glass panes are infused with gold dust, creating its sunlike golden color. The 4th Floor Observation Deck, operated by Visit Knoxville, is open to the public and offers 360-degree views of the surrounding area. The Sunsphere has become the most distinctive feature of Knoxville's skyline, standing alongside the Eiffel Tower (1889) and the Seattle Space Needle (1962) as a structure created specifically for a world's fair.