Mou Waho rises 140 metres from the floor of Lake Wānaka, a 120-hectare fragment of tussock and beech forest that predates human settlement by millennia. The island sits four kilometres offshore, visible from Wānaka township as a dark green silhouette against the Southern Alps. Glacial retreat 10,000 years ago shaped its ridgelines and left Arethusa Pool—a small tarn perched at 660 metres elevation, itself containing a tiny forested islet. The phenomenon of an island within a lake on an island within a lake draws geologists and photographers in equal measure. Since 1973, the Department of Conservation has maintained Mou Waho as a predator-free sanctuary. Stoat traps and bait stations ring the shoreline; no rats, possums, or mustelids survive here. Native buff weka, extinct on the mainland since the 1920s, were reintroduced in 1974 and now number over 200. The island also shelters grey teal, scaup, and South Island robin. In spring, tussock slopes bloom with Mount Cook lily and Celmisia daisies. The restoration work mirrors efforts on other Otago offshore islands but remains unusual for its accessibility—most predator-free reserves require helicopter transfers or multi-hour hikes. Water taxi services depart Wānaka Marina year-round, crossing open water in 25 to 30 minutes. The lake surface reflects weather patterns; morning departures benefit from glassy conditions before afternoon nor'westers build chop. Upon landing, a gravel track ascends through kanuka scrub and silver beech, gaining 140 metres over one kilometre to the Arethusa Pool viewpoint. The round-trip walk takes 45 minutes. Interpretive panels mark geological features and weka nesting sites. The island lacks facilities—no shelter, no toilets, no potable water—so visitors carry supplies and depart on scheduled return crossings. Mou Waho's isolation creates microclimates distinct from the lakeshore. Rainfall averages 200 millimetres higher than Wānaka township; snow dusts the summit in winter. The island's beech forest harbours fungi species rare on the grazed mainland. Conservation officers conduct quarterly weka counts and maintain the trap network through volunteer programmes. The site remains one of few places in Central Otago where pre-human ecology persists in functional form, offering a tangible measure of what the region's valleys once held.