These regions have different geographical structures. Whilst the Mostviertel is dominated by the foothills of the Limestone Alps with mountains up to m (AA) high, most of the Waldviertel is a granite plateau. The hilly Weinviertel lies to the northeast, descends to the plains of Marchfeld in the east of the state, and is separated by the Danube from the Vienna Basin to the south, which in turn is separated from the Vienna Woods by a line of thermal springs (the Thermenlinie) running north to south.