Oeschinensee is a turquoise lake at 1,578 metres held inside a rock amphitheatre. Cliffs rise almost sheer from the shore, and above them hang the glaciers of the Blüemlisalp massif, whose peaks climb past 3,600 metres. The meltwater off that ice carries the fine rock powder that turns sunlight into the lake's deep blue-green. The basin behind it was dammed by a disaster. A few thousand years ago a huge mass of the Doldenhorn broke loose and crashed into the valley, leaving well over a hundred million cubic metres of rubble as a natural wall. The lake also has no river running out of it — the water drains away into the loose rock beneath and resurfaces as a stream a few hundred metres downhill.
A gondola climbs from Kandersteg in about fifteen minutes. From the top station a half-hour path winds down through pine forest before the whole rock amphitheatre opens at once — sheer walls, hanging glaciers, still water far below. You can row a wooden boat across water cold enough to sting a bare hand in August, walk the shoreline loop, or ride a 750-metre summer toboggan run back toward the valley. In winter the surface freezes hard, and when conditions allow, marked routes are opened across the ice. Above it all, the crag called Spitze Stei has been creeping downhill since 2020 as the permafrost binding it thaws. Sensors measure every movement, and Kandersteg below keeps an alarm system ready to give residents at least 48 hours' warning, because the kind of collapse that created this lake could happen again on the peaks around it.