Thailand’s largest national park is home to at least 40 species of large mammal, such as tiger, leopard, elephant, gibbon, two types of Asiatic bear, and two types of leaf-monkey (langur). Established in 1981, this 1,150-sq mile (2,920-sq km) preserve covers nearly half of Phetchaburi province and contains some of the most pristine tracts of tropical evergreen forest in the country. The park is relatively unknown to tourists but offers some excellent hiking. Its western flank is marked out by the dramatic Tenasserim mountain range and the Thai Burmese border. Streams and rivers are the water source for the 17-sq mile (45-sq km) Kaeng Krachan reservoir, which can be explored by boat. Thousands of migratory birds coming from as far afield as China and Siberia rest, feed, and breed in the salt marshes.