The Park is part of the 2.5 million-hectare Tropical Rainforest Heritage of Sumatra, a World Heritage Site. It consists of steep, almost inaccessible mountainous terrain and encompasses smaller nature reserves. The Alas River runs through the Park and divides it into an eastern and western half. The Gunung Leuser National Park is known to be last place where orangutans, tigers, elephants, rhinoceros, and leopards lived together.