the Mun and to the west by tributaries of the Pa Sak River. History This whole mountainous region was covered by thick forest and was formerly known as Dong Phaya Fai or "jungle of the fire lord". There were no roads, hence it was not possible to use a cart. Travel across the forest had to be on foot or using palanquins. The whole area was reputed to be unhealthy and travelers who dared to pass through the woods exposed themselves to malaria and other illnesses. By the mid-19th century, when the clearing of the area began, Vice King (Uparaja) Pinklao changed the name of the forest from Dong Phaya Fai to Dong Phaya Yen to imply that "the wild forest had been tamed". By 1887 the Siamese government decided to build a railway line from Bangkok to Korat through Ayutthaya and commissioned British Railway contractors to make a survey. The first section of what is now the Northeastern Line, the railway line to Korat across the mountains opened in 1900. Much of the original forest cover of the mountains was destroyed since the beginning of 20th century. Following the completion of the line settlements were built in the area and trees were cut and land converted to agricultural use. Until quite recently only the railroad from Bangkok to Nakhon Ratchasima and one highway crossed the system. Deforestation increased as the building of more roads connecting central Thailand and Isan began in earnest. Thailand Route 2, also known as "Mittraphap Road", the main road crossing the range between Saraburi and Nakhon Ratchasima, was built in 1950. Protected areas These mountains, together with the Sankamphaeng Range at their southern limit, form the Dong Phayayen-Khao Yai Forest Complex, which includes several national parks. This area was inscribed on the UNESCO World Heritage List in 2005. Altogether 6,155 km2 are protected in the complex. In mid-2016 UNESCO briefly considered placing the Dong Phayayen-Khao Yai Forest on a list of endangered World Heritage sites because Thailand had not done enough to stop illegal logging of phayung (Siamese rosewood) trees. Other protected areas in the Dong Phaya Yen mountains are: Pa Hin Ngam National Park Sai Thong National Park Phu Khiao Wildlife Sanctuary Tat Ton National Park Nam Phong National Park Phu Lan Ka National Park, Sap Langka Wildlife Sanctuary Khao Somphot Non-hunting Area. Gallery See also Sankamphaeng Range References External links New Liphistius species