Around 2,200 years ago, an enormous section of hillside gave way. The resulting landslide dam, roughly 250 metres high, blocked the drainage and water began pooling behind it. Lake Waikaremoana is the product of that catastrophic collapse - one of relatively few landslide-dammed lakes anywhere in the world, and a rare example of one that proved stable enough to persist for millennia.

For most of the lake's history, water seeped through the porous landslip material rather than flowing cleanly over the top. It was not until the 1940s that engineers sealed the dam's lake side with 40,000 cubic metres of crushed rock and pumice, reducing the seepage by roughly 80 percent. Before that, the lake was slowly bleeding through its own walls.

The Waikaremoana Hydroelectric Power Scheme is a feat of engineering built on geological accident. Three power stations - Kaitawa, Tuai, and Piripaua - exploit a combined head of about 450 metres, generating up to 138 megawatts from a river flow of just 17 cubic metres per second. The Kaitawa station's 250-metre head is the highest of any power station in New Zealand and among the highest in the world.

Building it was an ordeal. Tunnelling through the unstable landslip began in 1935, only to be suspended in 1936 when Minister for Public Works Bob Semple questioned the project's risk, cost, and value. A revised tunnelling plan emerged in 1941, and construction resumed in 1943 - then dragged on for five years as workers fought constant problems dewatering the tunnels. The lake level had to be lowered with temporary siphons just to build the intake headworks. Every metre of progress was earned against geology that did not want to cooperate.

The Lake Waikaremoana Track follows roughly half the lake's circumference over three to four days, passing through forest that changes character with elevation - dense podocarp and broadleaf at the water's edge, beech forest climbing the ridges. Huts along the route require advance booking. Camping is permitted only within 500 metres of the track, a rule that keeps walkers from dispersing into backcountry that can turn dangerous quickly.

The weather is the kind that trampers learn to respect: temperate in summer, capable of snow in winter, and changeable enough at any time of year that hypothermia is a real risk for the unprepared. Heavy rain hits hardest in late winter and early spring. The track starts or ends at Onepoto, a village on the lake's southern shore whose name - 'short beach' - refers to a bay with a beach only 60 metres long. It is a modest portal to a walk that is anything but.

The lake lies within the boundaries of three iwi: Ngāi Tūhoe, Ngāti Ruapani, and Ngāti Kahungunu ki Te Wairoa. This is Tūhoe country - the 'Children of the Mist' - and the lake is bound up in their identity and their ongoing relationship with the Crown over Te Urewera. The smaller Lake Waikareiti, four kilometres to the northeast, adds another layer to the landscape: a companion lake in the same forested wilderness.

Aniwaniwa, a hamlet on the lakeshore, serves as the area's hub. A Department of Conservation office here coordinates the Great Walk and shorter excursions, including a stroll to Āniwaniwa Falls. State Highway 38 connects the lake to Rotorua to the northwest and Gisborne to the east, though 'connects' is generous for a road that remains largely unsealed. The journey is part of the experience - a gradual shedding of convenience that prepares you for a lake that offers beauty in exchange for effort.