Almost half of Hungary consist of plains and the highest level above the sea is 182 meters. The most important plain regions include the Little Hungarian Plain in the west, and the Great Hungarian Plain in the southeast. Transdanubia is a primarily hilly region, which include eastern stretch of the Alps, Alpokalja, in the west of the country, the Transdanubian Medium Mountains, in the central region of Transdanubia, and the Mecsek Mountains and Villány Mountains in the south. The highest mountains of the country are located in the Carpathian. Hungary is divided in two by its main waterway, the Danube; other large rivers include the Tisza and Dráva, while Transdanubia contains Lake Balaton, a major body of water. The largest thermal lake in the world, Lake Hévíz (Hévíz Spa), is located in Hungary.