Cambodia is a country located in the southern portion of the Indochina peninsula in Southeast Asia. Cambodia gained independence in 1953. The Vietnam War extended into the country with the US bombing of Cambodia from 1969 until 1973. Following the Cambodian coup of 1970 which installed the right-wing pro-US Khmer Republic, the deposed king gave his support to his former enemies, the Khmer Rouge. Historically the first major human evidence is that Iron was worked by about 500 BC, with supporting evidence coming from the Khorat Plateau, in modern-day Thailand. In 1993, Norodom Sihanouk was restored as King of Cambodia, but all power was in the hands of the government established after the UNTAC sponsored elections. Cambodia has a temperature range from 21 to 35 °C (70 to 95 °F) and experiences tropical monsoons. Cambodia's biodiversity is largely founded on its seasonal tropical forests, containing some 180 recorded tree species, and riparian ecosystems. The tourism industry is the country's second-greatest source of hard currency after the textile industry.