Now known as the Millennium Knickerbocker Hotel, this elegant Gothic Revival building houses a lavish space, especially the distinctive Crystal Ballroom, which features Chicago’s only illuminated dance floor. Well-known visitors to the hotel included Presidents Kennedy and Nixon, Muhammad Ali, and Daryl Hannah. Hugh Hefner purchased the building in the 1970s and transformed it into the Playboy Hotel. It was restored in 1999 by Millennium Hotels.