Switzerland is the moated castle of Europe. The great rivers of the continent have their source in the Alps: the Rhine flows into the North Sea, the Rhone into the Mediterranean, the Ticino flows into the Adriatic and the Inn into the Black Sea. For leisure and recreation, the more than 1500 lakes, the countless streams and rivers and the 1800 glaciers offer a variety of activities in spectacular natural landscapes that are probably unique in the world. The mountains are part of Switzerland's identity. The Alps and Pre-Alps cover two thirds of the country, and the main ridge with its 48 four-thousand-metre peaks forms the watershed of Europe. Summits such as the Matterhorn or the Eiger have become cult mountains for alpinists and guests from all over the world due to their grandiose shape and dramatic history. Switzerland is a green country. Forests cover a third of the total area and shape.