The Black Lake and the Devil's Lake

Cerne jezero, the Black Lake, lies in a glacial cirque under a steep wooded wall near Zelezna Ruda, and is the largest natural lake in the country, though at around eighteen hectares that is not saying a great deal. The water looks black because the cliff shades it and peat in the catchment absorbs the light rather than reflecting it. A path runs along part of the shore to a viewing spot; swimming and boats are not allowed, since the lake and its slopes are a strict reserve. Certovo jezero, the Devil's Lake, sits on the other side of the ridge, smaller and set even deeper in shadow, and the two are usually walked together on one circuit from the Spicak pass.

What's there

• Cerne jezero - the dark lake surface directly under a cliff wall several hundred metres high.
• Certovo jezero - the smaller second cirque lake over the ridge, quieter and harder to reach.
• The cirque wall - the steep rock and scree face left by ice, dropping straight into the water.
• The forest circuit - the marked path linking both lakes over the ridge from the Spicak pass.

When to go

May to October, when the paths are clear and the forest roads are walkable. Early morning gives the stillest water and the best reflections of the cirque wall. Autumn colour in the beech below the lakes is good. Snow closes the higher connecting path in winter, though the lower approach to the Black Lake stays usable on skis.

Things to know

You cannot swim, boat or picnic on the shore, and the viewing area is small and gets crowded at midday. The approach is a plain forest road with little to look at until you arrive. The lakes are dark and rather sombre in flat light, and photographs rarely convey the scale of the cliff. There is a hydroelectric installation nearby.

Nearby

Zelezna Ruda sits below, and the rest of the Sumava plateau spreads east toward Srni and Modrava.