Niagara Falls is the most powerful waterfall in North America, on the border between Ontario, Canada and New York State, where the water of four Great Lakes pours over a cliff at three thousand tonnes a second on its way to the fifth. It is not high, about 57 metres, but it is enormously wide, and what the crowd on the rail is watching is volume. There are three falls. American Falls and the small Bridal Veil are on the United States side; the Horseshoe, a curved wall of green water more than 800 metres around, is mostly Canadian, and the Canadian bank is where all three stack into one view along the riverside promenade. The boats are the classic way in: the Maid of the Mist from the American side and Niagara City Cruises from the Canadian ride right to the foot of the Horseshoe, into the cloud of mist where you cannot see, hear or stay dry.
At Table Rock, beside the Horseshoe, an elevator drops 38 metres through the rock into tunnels first cut in 1889 that end in openings directly behind the falling water, a wall of white noise a few metres from your face. Downstream, where the gorge bends and the river coils into a whirlpool, a cable car has crossed on six cables since 1916. After dark every night, projectors on the Canadian bank wash all three falls in shifting colour, and in winter the spray freezes on the rails and trees. The falls have a tap. Under a 1950 treaty, half the river is diverted to power stations at night and in winter, so the daytime summer flow is double what goes over on a December night. Twice the water has nearly stopped: for about thirty hours in March 1848, when an ice jam choked the river, and in 1969, when engineers dammed the American Falls to study the rock. In 1901 a 63-year-old schoolteacher, Annie Edson Taylor, went over the Horseshoe in a barrel and lived, the first person ever to do so, and Niagara has been daring people ever since.