There are a handful of routes to reach this remote inland sea but none are easy.

The most straightforward route is from Palmer Road but this requires a car shuttle. The shortest distance is via Rough Creek, which lives up to its name, tumbling down into the Maruia River over a steep staircase of boulders.

From the headwaters, a bit of grunt work is required to reach the treeline, where the stunted trees suddenly give way to a tussock basin. There’s no scrub to bash through here.

It should take about three hours to reach this point and gain views of the boomerang-shaped lake. It is the largest New Zealand lake still uncolonised by introduced fish. Long-finned eel and koaro (white bait), renowned for their ability to climb waterfalls, have penetrated the lake’s underground outlet. Since 1980, the lake has been protected as an ecological reserve.

Tiny tarns punctuate the sub-alpine basin here and would make idyllic campsites.

Follow the route down to the creek beneath The Grand Duchess, eventually reaching a well-graded track.

A swingbridge gives access to the eight bunk hut sited on a clearing by the Blue Grey River. All up, the trip up Rough Creek to hut should take between 6-9hr.

The following day, either retrace your steps or head out down the Blue Grey River, where you will have need to leave a car shuttle.