'Big Island' in the Mende language, 12-sq-km Tiwai Island certainly packs a punch when it comes to its primate population. Set on the Moa River, the entire island is run as a conservation research project. There are over 700 different plant species, 11 species of primates – including Diana monkeys and chimpanzees – 135 bird species plus otters, sea turtles and the endangered, elusive pygmy hippopotamus.

　　First you'll need to get to Poturu (there is regular transport from Bo or Kenema); from there you'll need an okada to Kambama. Speedboats (Le100,000 per person including island entrance fee) carry you the short distance to the island, where you can overnight in tents on canopied platforms (US$30), or in a bed at the simple research lodge (US$35) and drift off to sleep, listening to the midnight chatter of the rainforest.

　　Guided forest walks cost from Le25,000. Canoe tours cost Le50,000 per person.