Tenggarong, about 40 kilometres upstream from Samarinda, was the royal capital of the Kutai Kartanegara sultanate and is now a relaxed riverside town worth a day trip. The Mulawarman Museum, housed in the former sultan's palace on the Mahakam bank, holds a superb collection of Kutai royal regalia, Chinese trade ceramics, Dayak artefacts, and the Hindu stone sculptures associated with the ancient kingdom that flourished here fifteen centuries ago.
The town itself is pleasant to walk through: there are traditional Kutai wooden houses, a functioning sultanate palace that still hosts ceremonies, and a waterfront where you can hire a small boat to explore the Mahakam around Tenggarong. The annual Erau festival, held in September, is one of the great cultural events of Kalimantan — a week-long celebration of Dayak and Kutai traditions involving dance, ceremony, and river spectacle. The journey from Samarinda is about an hour by road or longer and more scenic by river.