Lake Cadagno

Lake Cadagno (Lago di Cadagno) sits in the Piora valley in the municipality of Quinto, canton of Ticino, Switzerland. At 1921 m above sea level in the Gotthard Massif near Airolo, it is one of the few meromictic lakes in Europe: its water layers do not mix. Scientists have studied it for years, and walkers find a quiet alpine shore with an easy loop trail.

What makes Lake Cadagno unusual?

The water divides into two zones. The upper one holds oxygen, while the deeper one has none and contains hydrogen sulfide. Roughly 10 to 13 m down, where the zones meet, a layer of purple-red sulfur bacteria forms, about 70 to 150 cm thick. In the dim light they convert toxic hydrogen sulfide into sulfate, which keeps it out of the oxygenated water above. The Piora valley has drawn researchers for more than two centuries, and the lake was once also used as a reservoir.

What can you see there?

The Alpine Biology Center stands on the shore. It hosts universities, polytechnics and secondary schools, and guided visits can be requested. An educational trail of about 4 km circles the lake on easy terrain, between 1912 m and 1964 m. Small stakes mark spots where microorganisms, or their effects on the environment, are visible, and the main information point is at the Center. The Capanna Cadagno hut offers meals and overnight stays.

How do you get to Lago di Cadagno?

The classic approach starts at Piotta, where the Ritom funicular climbs about 800 m on sections as steep as 87.8%. From Lake Ritom at the top, a trail leads on to Cadagno; Bellinzona's tourist office gives about 3 hours (roughly 10 km). Parking is available at the lower funicular station and by Lake Ritom itself in Piora. The funicular runs in season, typically from late May to mid-October.

When should you go?

Summer and early autumn work best, when trails are snow-free and the funicular and huts are open. Evenings are cool at this altitude, so pack an extra layer.

Frequently asked questions

Where is Lake Cadagno? In the Piora valley, municipality of Quinto, canton of Ticino, near Airolo, at 1921 m above sea level.

What does meromictic mean? The lake's water never fully mixes. The upper layer contains oxygen, and the deeper layer is oxygen-free and holds hydrogen sulfide.

Can you visit the research station? The Alpine Biology Center welcomes academic and school groups, and guided visits can be arranged on request.

Is the trail around the lake difficult? No. The loop is about 4 km with little elevation change (1912 to 1964 m) and is rated easy.