The trip to Lake Mavis begins at Greyneys Shelter on SH73. Use the pedestrian underpass and walk north along the 4WD track to cross the Bealey River just above its confluence with the Mingha. This trip has four river crossings and a couple of decent streams. If the Bealey looks doubtful, turn back and save it for another day. Do not use the railway bridge. 

The track up the Mingha Valley is straightforward and begins with easy tramping along river flats and through beech forest. It crosses the river twice before a short up and over Dudley Knob, which sidles the Mingha Gorge. At each end of the sidle are magical turquoise pools, rapids and waterfalls where you may spot whio. The summit of Dudley Knob offers rewarding views towards Goat Pass, with Mt Oates growing ever more present.

Mingha Bivouac, about an hour upstream, is perfectly sited in a clearing by the river. It’s very tidy, with a fireplace, two bunks and a north-facing window. I was a little sad to push on. However, a few minutes beyond is Kennedy Falls, a stunning 150m cataract that seemingly blasts from a hole in the hillside into the Mingha Valley. 

Cross the Mingha for the last time, and the vegetation opens into the alpine scrub and tussock of Goat Pass. There are stairs and boardwalks here protecting the sensitive alpine environment – all necessary, given the route is part of the Coast to Coast adventure race. 

On the wrong day this would be a wild and horrible place, so it’s worth knowing that Goat Pass Hut is a mere stone’s throw away over a lip into the Deception Valley. 

Look for a pair of cairns on the pass that mark the ground trail to Lake Mavis, initially up a steep scree slope, which is clearly visible from the boardwalks. After a solid 500m uphill slog, the trail reaches a spur and easier walking near the top of the scree. Allow two hours from Goat Pass to Lake Mavis.

Mavis fills an alpine bowl beneath the palisades of Mt Oates, and is one of those alpine lakes that’s impossibly clear, blue and beautiful. Snow and ice fall into the lake and float on the surface, and an impressive waterfall spills from its outlet. 

It’s a recognised camping spot, and a rock wall has been constructed to shelter tents. Kea may visit, so keep that in mind when you camp. 

Adventures beyond abound. Climb Mt Oates, or drop to Taruahuna Pass to link with the Otehake Valley or Edwards–Hawdon route. Serious climbers might tackle Mt Franklin. All are unmarked alpine routes, so navigation skills are essential. Crampons and ice axes may be necessary. 

For the rest of us, it’s time to return the way we came. A more ambitious exit is via the Deception Valley to Morrison’s Footbridge. This involves countless river crossings, and transport will need to be arranged.