Toronto's CN Tower is famous for its 553.3-metre communications antenna and overall height.
The tower was built by Canadian National Railway and opened to the public in 1976. Its main purpose was communications: Toronto's rapidly growing skyline was causing television and radio signal problems, so a very tall transmission structure was needed.
The CN Tower reaches 553.3 metres to the top of its antenna. Its concrete communications tower was the world's tallest free-standing structure from 1975 until 2007, when it was surpassed by Dubai's Burj Khalifa. The tower's height record is often discussed alongside skyscrapers, although the CN Tower is primarily a communications and observation tower rather than a conventional office building.
Visitors can use observation levels, including the Glass Floor and the 447-metre-high SkyPod. The EdgeWalk, introduced in 2011, lets participants walk around the outside edge of the main pod while secured by an overhead safety rail.
The name CN originally referred to Canadian National, the railway company that developed the project.