A region called Bohorok on the slope of Mount Leuser is one of the habitat of Orangutans. The government has declared this region as national reserve and a place to rehabilitate orangutans from their changing habit due to the domestication by people. Many of them confiscated from the private hobbiest or voluntarily give back to the government. Today only 3 places in the world still have this hominid heritages such as Indonesia in 2 places, which is the other one is on the island of Kalimantan, and other is on the continent of Africa. A trip to this region is available with pre-booked packages and can be found here.