At 553 m (1,815 ft) high, the CN Tower is the second-tallest free-standing structure in the world. In the 1970s, the Canadian Broadcasting Company (CBC) decided to build a new transmission mast in partnership with Canadian National (CN), the railroad conglomerate. The CN Tower was not originally designed as the world’s tallest spire, but it so overwhelmed the city’s visitors that it soon became one of Canada’s prime tourist attractions. The tower houses the largest revolving restaurant in the world, which rotates fully every 72 minutes.