One of the least explored areas on the planet, the mention of Borneo conjures up images of primeval rainforest, undiscovered tribes, and rare, exotic species. Comprised mostly of impenetrable jungle, the world's third-largest island is shared by Indonesia, Malaysia, and the tiny, wealthy Sultanate of Brunei. Home to critically endangered rhino, elephant, leopard, and orangutan – to name but a few – Borneo's wildlife is its top draw. But as pressures from logging, forest fires, and the growing demand for palm oil mount, refuges are increasingly the best way to see wildlife, so come while you can. While you're at it, take a trek up Sabah's Mt Kinabalu, search for the world's largest flower, or learn the ancient traditions of the island's headhunter tribes.