Bukit Lawang is the most popular base for organizing treks into the Gunung Leuser national park . The park around Bukit Lawang is actually a little over-trekked, and most serious walkers now prefer to base themselves in Ketambe in southern Aceh . But if you only want a short day-trek, a walk in the forest around Bukit Lawang is fine, and your chance of seeing monkeys, gibbons, macaques and, of course, orang-utans is very high. If you do decide to do a long trek from Bukit Lawang, the five- to seven-day walk to Ketambe is pleasant and passes through some excellent tracts of primary forest. The three-day hike to Berastagi is also very popular.

You must have a permit for every day that you plan to spend in the park. The PHPA office at Bukit Lawang recommends three local guides : Pak Nasib, Pak Mahadi and Pak Arifin. Their fees are higher than average, at approximately US$15 including lunch and permit for a one-day trek, but you can be certain that they know the forest well. Most of the other guides charge about Rp30,000 per day. Whoever you decide to hire, they shouldn't feed the orang-utans.

There are a couple of minor walks around Bukit Lawang that don't actually cross into the park, so permits and guides are unnecessary. The short, forty-minute walk to the Gua Kampret , Black Cave (Rp1000), is the simplest. It begins behind the Bukit Lawang cottages, across from the wartel on the north side of the river, and heads west through the rubber plantations, and, though it's easy, you'll still need good walking shoes and a torch if you're going to scramble over the rocks and explore the single-chamber cave.

By contrast, the path to the Panorama Point , in the hills to the east of Bukit Lawang, is difficult to follow. Most people take the path that begins behind the Back to Nature Guesthouse, though this can be tricky. A slightly easier route to follow - though much longer - is the path behind the Poliklinik near the visitor centre. It passes through cocoa and rubber plantations and, if you're successful, ninety minutes after setting out you should be able to gaze upon the valley of Bohorok.