Märjelensee

Märjelensee is a small lake above Fieschertal in the Swiss canton of Valais, sitting on the eastern edge of the Aletsch Glacier. What you see now is a remnant. In the 19th century this was one of the largest ice-dammed lakes in the Alps, and its sudden drainage threatened the Rhone valley.

What is Märjelensee?

The basin was carved by ice when a great arm of the Aletsch Glacier pushed towards the Fieschertal valley. A wall of ice held the water back. In the 1800s the lake measured roughly 1.6 km by 500 m, though Valais sources describe it as 2 km long and 25 m deep. It lies at about 46.44 N, 8.09 E, inside the UNESCO Swiss Alps Jungfrau-Aletsch area.

Why was the lake dangerous?

As the glacier shifted, meltwater found a channel beneath the ice and the lake could empty almost at once. The outbursts caused floods along the Rhone; one account says the water reached Sion. The same events fed a local legend about the Rollibock, guardian of the glacier.

What can you see today?

With the glacier in retreat, the big lake is gone. What remains is a small temporary lake known as Hintersee, about 100 m long, plus pools and bogs that turn white with cottongrass in autumn. From the Platta viewpoint you can judge how large the old lake was, and the Aletsch Glacier, the longest in the Alps, fills the view. The Gletscherstube Märjelen hut stands by the shore at roughly 2,363 m and is open from July to October. Since 1988 an artificial reservoir in the area has also supplied drinking and irrigation water to villages on the Aletsch plateau.

How do you get there?

Take the cable car from Fiesch via Fiescheralp to Eggishorn. The classic loop Eggishorn – Märjelensee – Fiescheralp is about 10–12 km, takes 3 to 4 hours and is graded medium. It passes Tälligrat and the little Tällisee, and on the way back you can walk through the lit Tälligrat tunnel. From Fiescheralp the hut is about 1.5 hours away via the upper Tälli and the tunnel.

When should you go?

Paths are best from July to September, and in good years into October. Carry a map, stay on marked trails and check the forecast, since mountain conditions change quickly.

Frequently asked questions

Is Märjelensee still a big lake?

No. The old lake vanished as the glacier retreated; a small lake and some ponds remain.

How long is the walk to the lake?

Usually 1.5–2 hours one way from Eggishorn or Fiescheralp, and 3–4 hours for the full loop.

Is there food nearby?

Yes, the Gletscherstube Märjelen hut serves hikers from July to October.

Why did the lake cause floods?

Its water could suddenly escape under the glacier ice and rush down into the Rhone valley.