mountain group, situated in extreme northern Bohemia, Czech Republic; it is part of the Sudeten mountains (Czech: Sudety). The group extends from the Ještěd ridge in the east (3,320 feet 【1,012 m】) to the gorge of the Elbe (Labe) River at Děčín in the west and also into Poland and Germany. Sandstone is the group's most common constituent rock, but there are also volcanic rock formations in conical hills. The Lusatian Mountains are separated from the Jizera Mountains (Jizerské hory) by the Neisse (Nisa) River.