1500 meters It is 1,500 feet tall as measured from the top of its antenna masts (457 m). The structure houses various businesses and restaurants, as well as around 700 condominiums, and at the time of its construction, it housed the world's tallest dwelling. It was built as a symbol of prosperity for the Chicago area and as an advertisement for the newly formed company John Hancock Mutual Life Insurance Company. Today, the antennas broadcast signals for radio frequency identification devices used by the United States Census Bureau to track the population distribution across the country. They also broadcast information relevant to the maintenance of the building's equipment, such as temperature changes inside its structure. The original design called for twin 1500-foot-tall towers with helical antennas spiraling up their sides. However, construction costs exceeded budget, so only one tower was built. The completed tower is 456 feet high and has 48 floors. It was designed by Mies van der Rohe and Cesar Pelli and opened in 1969. It was the first major commission for both architects. In addition to being a famous architectural landmark, the John Hancock Center is also known for being the home of the Chicago Bulls basketball team during the 1970s and 1980s. At the time, it was the largest arena in the NBA. The team moved out after the completion of the Chicago Stadium project in 1989.