Gelmersee, reservoir in the Bernese Oberland, Switzerland

Gelmersee is a mountain reservoir in the Swiss Alps near Grimselpass, surrounded by rocky terrain at high elevation. The water displays a bright blue-green color against steep mountain slopes over 10,000 feet (3000 meters) tall with no significant development nearby.

Gelmersee was built together with the Grimselsee reservoir, completed by 1929, and the Gelmer dam was finished in 1932; both are operated by Kraftwerke Oberhasli. The Gelmerbahn funicular, 1,028 m long with a maximum gradient of 106%, was built to carry workers and materials to the dam site. Water from the reservoir is used in the Handeck 1 power plant.

The white-red-white marked trail around the lake was cut into the steep rock face on the north shore, with the most exposed passages secured by ropes. The circuit takes about two hours and demands sure footing; it is unsuitable for small children, and during snowmelt streams can block the path.

The easiest access is via the Gelmerbahn funicular, which takes about eight minutes to climb, after which you can walk around the lake or do longer hikes. The best time to visit is from late spring through early autumn when weather is mild and trails are open; parking fills quickly during peak season so arriving early helps.

The Gelmerbahn funicular railway features slopes exceeding 100 percent in some sections, making it one of Europe's steepest, and offers spectacular views of waterfalls during the eight-minute ascent. The small cabins carrying only 24 passengers each move along twin tracks, creating an unexpectedly thrilling ride.