Milford Sound is a fifteen-kilometre fiord on the southwest coast of New Zealand's South Island, in Fiordland, where cliffs 1,200 metres high come straight out of the sea with no shore at their feet, and after rain the walls run with waterfalls from end to end. It is a fiord, not a sound: a glacier cut this trench below sea level and the ocean filled it when the ice melted, and the early sailors who named it simply got the word wrong. At its head stands Mitre Peak, 1,692 metres straight from the water and the most photographed mountain in the country, doubled in the fiord on a still morning. Rain falls here on about 182 days a year, close to seven metres of it, and this is not a reason to stay away: each heavy downpour sends hundreds of temporary waterfalls over the cliff edges at once, and the two permanent ones, Stirling and Bowen, are joined by a thousand others for a few hours.
The boat is the way to see it. Cruises run the full length to where the fiord meets the Tasman Sea, passing under the falls close enough for the spray to reach the deck, with fur seals resting on the rocks and bottlenose dolphins riding the bow wave; rare Fiordland crested penguins come ashore in July to nest, and their chicks are out on the rocks by spring. Guided kayaks set out from the head of the fiord early, when the water is at its calmest and the cliffs are silent apart from the falls. At Harrison's Cove a floating observatory lowers you ten metres beneath the surface into a round viewing chamber, and what you see there explains the fiord's strangest fact: a permanent layer of fresh water, stained dark by rainforest tannins, floats on top of the salt and blocks so much light that black coral and other deep-sea creatures live within reach of a snorkel. Rudyard Kipling called Milford Sound the eighth wonder of the world, and the rain is part of the wonder.