Ryžovna, Nature reserve in Ostrov, Czech Republic.

Ryžovna is a 20-hectare nature reserve on a basalt plateau at about 1,000 m in the western Krušné hory, 3 km north of Abertal. Two disused quarries cut the ridge between Ryžovna and Hřebečná: the southern one exposes coarse basalt columns 50–80 cm across, the northern one platy to blocky basalt.

The reserve was declared in 1996 to protect the basalt cap and the mountain bog communities of the Klínovec highlands. Two quarries on the ridge between Ryžovna and Hřebečná, idle since 1960, had already exposed the rock. Military radio-survey buildings erected around 1961 stood on the site, abandoned by the Czechoslovak army in 1969 and used by Red Army troops from 1984 to 1988.

The reserve lies above the abandoned settlement of Ryžovna (German: Seifen), about 3 km north of Abertam. A mountain nature trail from Hřebečná to Ryžovna, focused on the history of mining, ends at the larger of the two quarry walls.

Access is via an asphalt road branching off the Ryžovna–Hřebečná road, ending at the former 1961 military radar site. The Hřebečná–Ryžovna educational trail, focused on mining history, leads to the larger quarry wall and ends there, with information boards along the way.

Two former quarries less than 200 m apart expose the same basalt with contrasting jointing: coarse columns 50–80 cm wide on the south slope, slabby blocks on the north. The south quarry wall is a geological site of the Egeria Geopark.