The apex is occupied by a massif of crystalline rocks.
These two channels carry the rush of mountain streams from the western slopes of the massif right across the axis of the mountains and through the intervening barrier of minor ridges to the plains of the Indus.
The cordilleras, divided into two great parallel chains, with flanking ranges and spurs to the east, reach their greatest breadth at this point and form the massif of the Andean system.
The northern part (Czech Cesky Les) attains in the massif of Czerkov an altitude of 3300 ft., but the southern part (Czech Sumava) is at the same time the highest and the most picturesque part of the range, including on the Bohemian side the Osser (4053 ft.) and the Plockenstein (45 1 3 ft.), although the highest peak, the Arber (4872), is in Bavaria.
The mountain-ranges of the interior of Bohemia are the Brdywald (2798 ft.) in the middle; the Tepler Gebirge (2657 ft.), the Karsbader Gebirge (3057 ft.) and the Kaiserwald (3238 ft.), in the north-west part; while the northern corner is occupied by the Mittelgebirge (2739 ft.), a volcanic massif, stretching on both sides of the Elbe.
