Gunung Leuser National Park

Gunung Leuser covers a huge stretch of rainforest along the spine of northern Sumatra and is one of the last places where wild Sumatran orangutans can be seen. Most visitors arrive at Bukit Lawang, a riverside village on the park's eastern edge, and walk into the forest with a licensed guide for anything from a few hours to several days. The orangutans here are a mix of genuinely wild animals and descendants of rehabilitated ones, so sightings are common but never guaranteed. The forest also holds gibbons, Thomas's leaf monkeys, hornbills and, in numbers almost nobody ever sees, elephants and tigers. Nights are spent in simple camps by the Bohorok river, and many people float back out on inner tubes.

What you actually see

• Sumatran orangutans - the great apes tracked on foot in the forest above Bukit Lawang.
• The jungle trek - day walks or multi-day routes with camps beside the river.
• Bohorok river tubing - the standard way back to the village, floating on an inner tube.
• Other primates - Thomas's leaf monkeys, macaques and gibbons heard before they are seen.

When to go

The drier months from May to September make the trails less slippery and river levels more predictable, though rain is possible any time in a rainforest. Mornings are best for primate activity. Book a guide through a registered agency rather than on the street, and settle the route, meals and permit fee before setting off.

Honest expectations

Bukit Lawang is busy and the same trails carry a lot of groups, so quiet forest is rarer than the photos suggest. Some guides still feed orangutans or crowd them for pictures, which is bad practice and worth refusing. The walking is steep, humid and muddy, leeches are normal, and one habituated female has a reputation for aggression.

Nearby

Lake Toba lies south, and Medan is the usual gateway city.