Milford Sound catches more than six metres of rain a year, and that soaking is the whole attraction: after a heavy storm, hundreds of temporary waterfalls burst at once from cliffs that rise more than 1,200 metres straight out of the water. The 15-kilometre inlet was gouged by glaciers and later drowned by the Tasman Sea, which makes it a true fiord rather than the "sound" its name claims — a label left by the Welsh sealer John Grono, who named it for Milford Haven back home after Captain Cook had sailed past the hidden entrance twice. Māori knew it long before as Piopiotahi, and today it anchors Te Wāhipounamu, a UNESCO World Heritage area. Guarding the head of the fiord is Mitre Peak, a sheer 1,692-metre pyramid that is the most photographed mountain in the country.
Rain falls here on about 182 days a year, and the fiord looks its best soaking wet: the two permanent falls, Lady Bowen and Stirling, thunder down more than 150 metres all year, while the temporary ones lace the dark walls with silver and drain away within hours of the clouds parting. On the rare windless day the water settles into a flawless mirror of the peaks. Boats run to the foot of the cliffs, close enough to catch Stirling Falls' spray, past fur seals hauled out on the rocks and pods of bottlenose dolphins. Stranger still is what hangs just below the surface: a dark layer of freshwater, stained by rainforest tannins, filters the light so heavily that deep-sea black coral grows within ten metres of the top, visible from an underwater observatory at Harrison's Cove. Nearly everyone reaches all this through the Homer Tunnel, a raw 1.2-kilometre bore driven through solid rock and opened in 1954 — still the only road in.