Tannabalu, the highest point at 620 metres (2,030 ft), is a conical, extinct volcano located at the centre of the island.

The south side of the island is only separated from the mainland by a shallow channel known as the Trusan Sigalong.

In addition there are newer, illegal settlements which have sprung up on the southeastern portion of the island.

The island was declared a forest reserve in 1930, but had been planted in teak as early as the 1880s.

The teak forests have been periodically surveyed, but inroads by illegal logging and land clearing has reduced them.