Gerecse is a heavily faulted block mountain of the Transdanubian Range, made up of karstified rocks of limestone and dolomite. It is the westernmost triangular region of the Dunazug Mountains. Its four hilly ranges reach the Danube. Its average height is 400 metres, its area is 850 km², and its highest peak is the 634-metre-high Gerecse Peak. The approximately 400 m deep wells from where VIVIEN natural mineral water is drawn, are located in the lower elevation, exposed Triassic dolomite embayments of the Gerecse and Vértes Mountains.