Eibsee is a lake you can see the bottom of. It lies in Bavaria under the north face of the Zugspitze, Germany's highest mountain, and the floor under its shallows is pale gravel, so the water reads green and the stones stay visible metres down. Then the colour changes. Where the basin drops away the green deepens and the bottom is gone. Almost all of it came off the mountain above. About 3,700 years ago a slab broke away from the Wetterstein walls and ran down the valley, and the blocks that stopped in the water are still there — wooded islets that grew pines. You can row out between them from the boathouse, the bottom falling away under the hull as you go, and once clear of the pines the whole wall gathers into one frame.
A path of seven and a half kilometres takes you round the shore in about two hours, the Zugspitze appearing and disappearing behind the trees, gravel coves opening one after another. Three bays on the south side shelve gently over pale stones, warm enough in a hot July to climb past twenty degrees — which almost no other alpine lake manages. You wade in and can still see your feet at chest depth. A few steps further the floor drops and the cold comes straight back. The cable car leaves from the shore and gains nearly two thousand metres, and on the way up the lake shrinks to a bright sheet, the islets reduced to green dots. Through October the beech and larch around it turn copper and gold, the still surface doubles them, and the summit takes its first snow. Then the whole thing freezes under half a metre of ice. The name is older than any of it: Eibe is German for yew, a tree that has almost left the bank. The lake holds on to none of it. Meltwater lifts the level close to two metres by late summer and the gravel beaches narrow, and then the whole of it drains away again through the limestone floor it is standing on.