Gunung Leuser National Park is one of the biggest national parks in Indonesia (950,000 hectare). Actually it is a collection of various nature reserves and forests. The Alas river cuts the park into eastern and western halves. It consists of steep, almost inaccessible mountainous terrain. The altitude ranges from 0 meters to 3,381 meters. Apart from mountains, several other ecosystems beach forest, swamp areas, lowland rainforest, alpine and mountain forest are found. Because of the great differences in altitude and the diversity in soil, the Gunung Leuser National Park has an enormous wealth of plant species.