Niagara Falls

Horseshoe Falls is only 57 metres high, but with roughly 2,800 cubic metres of water per second it ranks among the world's highest-volume waterfalls. The rock face erodes constantly, so the falls retreat about thirty centimetres a year — three times faster before water was diverted for hydroelectric power. In 1969 engineers built a temporary cofferdam on the American side to inspect the bedrock and stopped the falls completely for months. In 1901, sixty-three-year-old schoolteacher Annie Edson Taylor became the first person to survive going over the falls inside a barrel.