Colourful weekly markets are held each Friday in the bus station at Gotong Royong, where buses from Medan drop and pick up passengers. It's a fifteen minute walk from the bottom of Bukit Lawang itself, and a reasonable walk, although locals nearly all go by motorbike or becak (motor rickshaw), fare, 5,000rp per person, and might think you crazy if you prefer to walk in the heat.
If you are in town on a Friday, it's worth a visit. The market runs from morning until around 4pm. If you arrive in the morning you will see workers from local rubber plantations bringing their rubber to be weighed and sold. By afternoon all the rubber will have been sold, and the workers and land owners paid, but the strong smell will remain!
Vendors in the market include: fish sellers, meat sellers, many different fruit sellers, vegetable sellers, spice and jamu (traditional medicine) sellers, people selling dried fish and shrimp, clothes (mostly used and of very low cost and basic quality), household goods, fireworks, and others.
On days other than Friday two or three vendors sell fruit and vegetables in the same venue.
A similar, slightly larger, market is held in Bohorok the town 11km from Bukit Lawang on Sundays.
If you would like a guide to visit the Friday Gotong Royong market and do a two hour tour explaining the different kinds of fruit, vegetables, fish, spices and other items on sale, the cost will be 200,000rp for up to three people inclusive of round-trip becak trip.
For the same kind of tour at Sunday's Bohorok market, the cost is 200,000 rupiah for one person, by motorbike taxi, or 300,000 rupiah for two people by becak.