Sinharaja

Sinharaja is the largest remaining area of primary rainforest in Sri Lanka, and a UNESCO World Heritage Site for it. It's quiet, humid, and genuinely wild compared to the more visited parks — a local tracker-guide is required to enter, and walks through the reserve turn up endemic birds, giant squirrels, and if you're lucky a mixed-species feeding flock, one of the reserve's best-known sights. It's a detour rather than something on the main route, so it suits travellers with a real interest in nature and time to spare.