Kum Kum is a small riverside zoo and rescue centre on the eastern side of the Kahayan, reached by a short boat ride from town. It houses confiscated and orphaned Borneo wildlife — orangutans, sun bears, proboscis monkeys, hornbills — in conditions that are workmanlike rather than luxurious.
For a closer look at species you'll struggle to see in the wild on a short visit, it's the practical option. Standards vary; ask around before going.