Where? Sarawak, Malaysian Borneo
By night in this nine-square-mile national park you’ll spot fireflies dancing over the Batang Ai and Lubang Baya rivers, then, by day, there’s the orangutans. In fact, Batang Ai has the highest orangutan population density in central Borneo, making your chances of seeing one in the wild pretty high. That said, you must undertake some of the park’s four hikes if you have any hope of a sighting – be sure to hire a ranger and bring plenty of food and drink before embarking on your trek.