Dominica is rich in natural beauty, with waterfalls, rivers, tropical rainforest and numerous rare plants and wildlife. Some of the most popular sights include Emerald Pool, Trafalgar Falls and the World Heritage Site of Morne Trois Pitons Park, a volcanic region with some of the world's largest boiling mud ponds. Offshore, nature lovers might spot up to six species of dolphin, and perhaps killer or humpback whales.