Jezerka is a national nature reserve in the Ore Mountains (Krušné hory), where a steep, rocky slope hides the remains of a medieval castle, rock towers and a deep valley cloaked in old beech forest. It's a place for those seeking wild, largely untouched nature right at the edge of a brown coal mine.

The reserve's landscape is shaped by the 250-metre-deep valley of the Vesnický Brook and the steep, rocky slope rising toward the summit of Jezeří. In spring and summer the forest comes alive with birdsong from red-breasted flycatchers and golden orioles, while peregrine falcons nest on the cliffs. In autumn the beech woods turn gold, and in winter the area is often shrouded in temperature-inversion fog typical of this part of the Ore Mountains. Rock formations - towers, bastions and balancing boulders - give the place a rugged, almost alpine character despite its modest elevation.

• Vysoká Pec - yellow trail to Jezeří Castle along the reserve's southeastern edge, easy to moderate difficulty
• A branch of the blue trail between Jezeří and Lesná leads to the summit
• A service road along the western and northern boundary from Vysoká Pec gives access to the Terezina vyhlídka viewpoint

• Rock climbing has been banned in the reserve since 1992
• The former blue nature trail was decommissioned and parts of the path have collapsed
• The area is only partly accessible via marked hiking trails

On the southern ridge of Jezeří stands a striking balancing rock shaped like a human head, and nearby lies a crevice cave known as Na Jezeří - proof of how frost and gravity can carve fantastic shapes into rock.