Ratchaprapa Dam, built in a part of Khao Sok National Park, which is one of the world’s oldest rainforest, closes off the Pasaeng river, creating a 185 square kilometre lake. It has been a main source of power generating in the south of Thailand for nearly 30 years. The emerald green color of the water is the result of the sunlight reflecting off the algae underneath it. The surrounding 165 karsts hills were the tips of the mountains themselves before the dam was built. The limestone karsts are the deposits from 280 million years ago which began to form as the marine life established a long coral reef that stretches from China, passing Halong Bay via the south of Thailand to Sarawak State of Borneo Island. Hidden in these hills are beautiful caves, wild animals such as hogs, gaurs and various types of birds, all foraging at dawn and twilight.