Sinharaja Rain Forest a very important, UNESCO named world heritage site and Biosphere reserve. Sinharaja is one of the most important bio diversity hotspot in Sri Lank The hilly virgin rain forest, part of the Sri Lanka lowland rain forests was saved from the worst of commercial logging by its inaccessibility, it is a treasure trove of endemic species, including trees, insects, amphibians, reptiles, birds and mammals.

An interesting phenomenon is that birds tend to move in mixed feeding flocks, invariably led by the fearless Greater Racket-tailed Drongo and the noisy Orange-billed Babbler. Of Sri Lanka's 26 endemic birds, the 20 rainforest species all occur here, including the elusive Red-faced Malkoha, Green-billed Coucal and Sri Lanka Blue Magpie.

Reptiles include the endemic Green pit viper and Hump-nosed vipers, and there are a large variety of amphibians, especially tree frogs. Invertebrates include the endemic Common Birdwing butterfly and the inevitable leeches.