The Gunung Leuser National Park, named after its highest peak, the 3,381-meter Mount Leuser, was originally established as a wildlife reserve. Alongside Kerinci Seblat and Bukit Barisan Selatan National Parks, it forms part of the UNESCO World Heritage site known as 'The Tropical Rainforest Heritage of Sumatra' since 2004.
 
In 1973, a Swiss organization established an orangutan rehabilitation center in Bukit Lawang (which means "door to the hills") to rehabilitate orangutans released from captivity. The center's rangers teach these orangutans essential survival skills. Following a period of quarantine, habitat readjustment, and reintegration into the (semi-)wild population, the orangutans are released back into the jungle. The rangers continue to monitor them and provide supplementary food at the feeding platform until they become fully self-reliant. 
 
Due to the presence of the rehabilitation center, Bukit Lawang became a popular destination for tourists. Although the feeding center has been closed and all orangutans have been released into the wild, you can still see orangutans while trekking in the national park with a guide.