No river runs out of Lake Oeschinen. It is held in a bowl of cliffs above the village of Kandersteg, in the Bernese Alps, under the hanging glaciers of the Blüemlisalp, and it is there because a mountain came down. A vast rockslide off the Doldenhorn dammed this valley thousands of years ago, and the water behind the rubble has been leaking through it ever since. It leaks slowly. The level rises and falls by several metres across the year, so the shoreline moves in and out, and what stays behind is exceptionally cold and clear. The colour comes off the ice above: from June to September the melt carries fine rock powder in and turns the water its deepest blue-green, paling to grey either side of that. The cliffs stand two thousand metres over the surface with waterfalls coming off them in threads.
The shoreline loop rings the lake in about two hours, through pine forest and open alp with the cliffs mirrored beside you. Dairy cattle graze the lakeside meadows all summer, their bells carrying across the basin. Wooden rowboats go out from the jetty, and a hundred strokes from shore the cliffs close the whole horizon above you. The water comes straight off the glaciers, so a swim in an August heatwave is still icy. A mountain inn on the shore keeps rooms, and whoever takes one gets the lake at first light, dead calm, the Blüemlisalp doubled on it. From the top station a 750-metre toboggan track drops through 150 metres of curves with the mountains ahead of you, and you set your own speed on the brake. The slopes above have not settled. Since 2020 the crag of Spitze Stei has been sliding as the permafrost binding it melts, at times seventy centimetres in a day. What finally works its way out through the rubble surfaces again a few hundred metres downhill as a stream called the Oeschibach, by which time it has spent the better part of two years inside the lake.