Laos is the only landlocked country in Southeast Asia. It lies mostly between latitudes 14° and 23°N (an area is south of 14°), and longitudes 100° and 108°E. Its forested landscape consists mostly of mountains, the highest of which is Phou Bia at 2,818 metres (9,245 ft), with some plains and plateaus. The Mekong River forms a part of the western boundary with Thailand, where the mountains of the Annamite Range form most of the eastern border with Vietnam and the Luang Prabang Range the northwestern border with the Thai highlands. There are two plateaus, the Xiangkhoang in the north and the Bolaven Plateau at the southern end. Laos can be considered to consist of three geographical areas: north, central, and south.[21] Laos had a 2019 Forest Landscape Integrity Index mean score of 5.59/10, ranking it 98th globally out of 172 countries.[22] In 1993, the Laos government set aside 21% of the nation's land area for habitat conservation preservation.[23] The country is one of four nations in the opium poppy growing region known as the "Golden Triangle".[24] According to the October 2007 UNODC fact book Opium Poppy Cultivation in South East Asia, the poppy cultivation area was 15 square kilometres (5.8 sq mi); this is down from 18 square kilometres (6.9 sq mi) in 2006.[25] Climate[edit] Köppen climate classification map of Laos The climate is mostly tropical savanna and influenced by the monsoon pattern.[26] There is a rainy season from May to October, followed by a dry season from November to April. Local tradition holds that there are three seasons: rainy, cool and hot. Further, the latter two months of the climatologically defined dry season are hotter than the earlier four months.[26] Wildlife[edit] Main article: Wildlife of Laos Laos, with its forests and river systems, is home to an amount of wildlife.[27][28] National parks like Nam Et-Phou Louey are critical refuges, supporting endangered species such as the northern white-cheeked gibbon and the saola.[29] These forests shelter more than 50 mammal species and nearly 300 bird species, along with a variety of reptiles and amphibians.[c] Administrative divisions[edit] Main article: Administrative divisions of Laos Laos is divided into 17 provinces (khoueng) and one prefecture (kampheng nakhon), which includes the capital city Vientiane (Nakhon Louang Viangchan).[30] No. Subdivisions Capital Area (km2) Population 1 Attapeu Attapeu (Samakkhixay district) 10,320 114,300 2 Bokeo Houayxay (Houayxay district) 6,196 149,700 3 Bolikhamsai Paksan (Paksane District) 14,863 214,900 4 Champasak Pakse (Pakse District) 15,415 575,600 5 Houaphanh Xam Neua (Xamneua District) 16,500 322,200 6 Khammouane Thakhek (Thakhek District) 16,315 358,800 7 Luang Namtha Luang Namtha (Namtha District) 9,325 150,100 8 Luang Prabang Luang Prabang (Luang Prabang district) 16,875 408,800 9 Oudomxay Muang Xay (Xay District) 15,370 275,300 10 Phongsaly Phongsali (Phongsaly District) 16,270 199,900 11 Sainyabuli Sayabouly (Xayabury District) 16,389 382,200 12 Salavan Salavan (Salavan District) 10,691 336,600 13 Savannakhet Savannakhet (Khanthabouly District) 21,774 721,500 14 Sekong Sekong (Lamarm District) 7,665 83,600 15 Vientiane Prefecture Vientiane (Chanthabouly district) 3,920 1,001,477 16 Vientiane Province Phonhong (Phonhong District) 15,927 373,700 17 Xiengkhouang Phonsavan (Pek District) 15,880 229,521 18 Xaisomboun Anouvong (Anouvong district) 8,300 82,000 An updated map of Lao provinces (from 2014) History[edit] Main article: History of Laos Prehistory[edit] In 2009, a human skull was recovered from the Tam Pa Ling Cave in the Annamite Mountains in northern Laos; the skull is at least 46,000 years old, making it the oldest modern human fossil found to date in Southeast Asia.[31] Stone artifacts including Hoabinhian types have been found at sites dating to the Pleistocene in northern Laos.[32] Archaeological evidence suggests an agriculturist society developed during the 4th millennium BC.[33] Burial jars and other kinds of sepulchers suggest a society in which bronze objects appeared around 1500 BC, and iron tools were known from 700 BC. The proto-historic period is characterised by contact with Chinese and Indian civilisations. According to linguistic and other historical evidence, Tai-speaking tribes migrated southwestward to the territories of Laos and Thailand from Guangxi sometime between the 8th and 10th centuries.[34] Lan Xang[edit] Main article: Lan Xang Laos traces its history to the kingdom of Lan Xang ('million elephants'), which was founded in the 13th century by a Lao prince, Fa Ngum,[35]: 223  whose father had his family exiled from the Khmer Empire. Fa Ngum, with 10,000 Khmer troops, conquered some Lao principalities in the Mekong river basin, culminating in the capture of Vientiane. Ngum was descended from a line of Lao kings that traced back to Khoun Boulom.[36] He made Theravada Buddhism the state religion. His ministers, unable to tolerate his ruthlessness, forced him into exile to what is later the Thai province of Nan in 1373,[37] where he died. Fa Ngum's eldest son, Oun Heuan, ascended to the throne under the name Samsenethai and reigned for 43 y