Gunung Leuser National Park

Gunung Leuser National Park is the last stronghold where Sumatran orangutans, tigers, rhinos, and elephants coexist in a single ecosystem—a feat no other park on this list can claim. Spanning 1.1 million hectares across the Leuser Ecosystem, it contains peat swamp forests that store 40% more carbon per hectare than the average tropical rainforest. Over 300 bird species have been recorded here, placing it ahead of #4 Ujung Kulon in avian diversity. The park’s orangutan population exceeds 8,000, making it the world’s largest contiguous wild population, and its lowland forests are 25% denser than those in Tanjung Puting. Visitors often trek for three to five days to spot wildlife, with success rates reaching 85% for orangutan sightings during peak season.