What makes Milford Sound worth the trip?
Milford Sound (Piopiotahi in te reo Māori — the place where the piopio bird was lost) occupies the most north-westerly extremity of Fiordland National Park, a 1.2 million-hectare UNESCO World Heritage Area that encompasses fourteen fiords carved into the ancient Fiordland granite by successive ice ages over the past 2 million years. The Sound is technically a fiord (carved by glaciers rather than eroded by rivers), and at 22 kilometres in length with vertical cliff walls reaching 1,200 metres above sea level — among the highest coastal cliffs in the world, with Mitre Peak rising to a summit of 1,692 metres — it is simultaneously the most dramatic and the most accessible of Fiordland's fourteen glacial inlets.
The walls of the fiord are permanent waterfalls. Stirling Falls drops 151 metres in a single uninterrupted cascade that cruise boats pass close enough to feel the spray; Bowen Falls at 162 metres tumbles from a hanging valley above the Sound's terminal moraine. After heavy rain, these permanent falls multiply into hundreds — temporary cataracts appearing from every crease in the cliff face, feeding the distinctive dual-water effect where a layer of dark, peat-stained fresh water floats over the underlying salt water for 10 metres depth, creating conditions that allow deep-sea species to live at snorkel depth and are studied by marine biologists from the nearby Piopiotahi Marine Reserve research station.
The journey from Queenstown to Milford is itself a 5-hour scenic experience of extraordinary quality — the road passes through the Eglinton Valley's beech forest, over the Divide saddle, and through the Homer Tunnel (a 1.2-kilometre bore through solid granite drilled by hand during the 1930s Depression) to emerge on the western side of the main divide into Fiordland's permanent temperate rainforest, where the landscape shifts from pastoral to primordial in the space of a few kilometres.