Highest external walk on a building

The highest external walk on a building is located 356 m (1,167 ft 11.72 in) above the ground, running full-circle around the top of the CN Tower's restaurant in Toronto, Canada. Participants experience a "hands-free", harness-secured “edgewalk” along a 150-m-long (492-ft) ledge just 1.5 m (5 ft) wide. The CN Tower is a communications and observation tower which rises to 553.34 m (1,815 ft 5 in). Topped out on 2 April 1975, the 130,000-tonne reinforced, post-tensioned concrete CN Tower was the world's tallest building and tower until the completion of the Burj Khalifa Tower and Canton Tower respectively. Its name "CN" originally referred to Canadian National, the railway company that built the tower.