Cambodia occupies 181,035 square kilometers on the Indochinese Peninsula between Thailand, Laos, and Vietnam. The Mekong River bisects the country north to south, carrying 475 cubic kilometers of water annually through the central plains. Tonle Sap Lake expands from 2,500 square kilometers during dry season to 16,000 square kilometers when monsoon rains reverse the Tonle Sap River flow between June and October. This hydrological phenomenon sustains the largest freshwater fishery in Southeast Asia, producing roughly 300,000 metric tons of fish annually and making aquatic protein foundational to Khmer diet. The Cardamom Mountains in the southwest reach 1,771 meters at Phnom Aural, creating a spine of rainforest that holds the last viable populations of Indochinese tigers and Asian elephants in the region. The country's 443-kilometer coastline along the Gulf of Thailand remains less developed than neighboring coasts, with Koh Rong Island and Koh Rong Samloem hosting coral reefs that attract hawksbill turtles and whale sharks during April to June migrations.
The Khmer Empire governed much of mainland Southeast Asia between 802 and 1431, building a sophisticated hydraulic civilization around Angkor that may have supported one million people at its peak in the twelfth century. Suryavarman II commissioned Angkor Wat starting in 1113 as a temple dedicated to Vishnu, constructing the largest religious monument on Earth with a 1,500-meter perimeter wall enclosing 162.6 hectares. The central tower rises 65 meters above ground level, aligned to place the sun directly above the structure during spring equinox. Jayavarman VII built Angkor Thom and the Bayon Temple in the late twelfth century after reclaiming the capital from Cham invaders, installing 216 serene stone faces across 54 towers that scholars identify as representations of Avalokiteshvara or possibly the king himself. The empire collapsed during the fifteenth century due to factors historians continue debating—environmental degradation from deforestation, overextension of irrigation systems causing salinization, trade route shifts favoring coastal ports, or repeated Thai invasions. The capital relocated to Phnom Penh in 1434, where it has remained except for brief periods.
France established a protectorate in 1863 under King Norodom I, administering Cambodia as part of French Indochina until 1953. King Norodom Sihanouk negotiated independence peacefully on November 9, 1953, after threatening to join the Viet Minh if France refused. Cambodia maintained neutrality during the early Vietnam War until 1970, when General Lon Nol overthrew Sihanouk in a coup backed by the United States. American B-52 bombers dropped approximately 2,756,941 tons of ordnance on Cambodian territory between 1965 and 1973, primarily targeting Vietnamese supply routes but killing an estimated 150,000 to 500,000 Cambodian civilians according to Yale University's Cambodian Genocide Program. The Khmer Rouge under Pol Pot seized Phnom Penh on April 17, 1975, immediately evacuating the city's two million residents to rural labor camps. The regime killed an estimated 1.7 to 2.2 million people between 1975 and 1979—roughly one quarter of Cambodia's population—through execution, starvation, disease, and overwork. Vietnamese forces invaded in December 1978, establishing the People's Republic of Kampuchea and driving Khmer Rouge remnants to the Thai border. Civil war continued until the Paris Peace Accords of October 23, 1991, followed by United Nations supervision of elections in May 1993 that returned Sihanouk as constitutional monarch.
This historical sequence remains visible in contemporary Cambodia in ways that shape every visitor encounter. Tuol Sleng Genocide Museum preserves Security Prison 21, where Khmer Rouge interrogators documented 14,000 prisoners before sending them to Choeung Ek killing fields fifteen kilometers south of Phnom Penh. The museum maintains original torture implements, mugshots of prisoners, and regulations painted on classroom walls converted to cells. Choeung Ek displays 8,985 skulls in a memorial stupa, representing a fraction of the 1.38 million victims whose remains have been exhumed from 388 mass grave sites across Cambodia according to the Documentation Center of Cambodia. Younger Cambodians born after 1979 now constitute 65 percent of the population, creating a generational divide between those who remember the Khmer Rouge era and those who know it only through education and family stories. The Extraordinary Chambers in the Courts of Cambodia, established in 2006 with UN support, convicted Khmer Rouge leaders Nuon Chea and Khieu Samphan of crimes against humanity in 2014 and genocide in 2018. Both died during subsequent appeals, Nuon Chea in 2019 at age 93 and Khieu Samphan remains imprisoned at age 93 as of 2024.
Angkor Archaeological Park attracts more visitors than any other site in Cambodia, recording 2.1 million international tourists in 2019 before pandemic closures. The park covers 400 square kilometers containing remains of multiple Khmer capitals built between the ninth and fifteenth centuries. Ta Prohm remains partially unrestored since French archaeologists began conservation work in 1898, with silk-cotton trees and strangler figs growing through galleries and towers in photogenic entanglement. Banteay Srei lies 25 kilometers northeast of the main temple group, built in 967 from pink sandstone with devata carvings that retain detail finer than any other Angkor structure due to the dense stone composition. Preah Vihear Temple occupies a 525-meter cliff on the Dângrêk Mountains along the Thai border, built during the eleventh century with successive gopura gates ascending the escarpment. The International Court of Justice awarded sovereignty to Cambodia in 1962, though border tensions caused firefights as recently as 2011 before both countries accepted UNESCO monitoring. The Angkor ticket system generated $116 million in revenue during 2019, split between the government-contracted operator and the APSARA Authority responsible for preservation.
Siem Reap serves as the base for Angkor visits, growing from a town of 85,000 in 2000 to approximately 250,000 residents by 2020. The airport processed 2.6 million passengers in 2019, making it Cambodia's busiest despite Phnom Penh's larger metropolitan population of 2.3 million. Chinese investment has concentrated in Siem Reap Province since 2016, building casino resorts and entertainment complexes that stand largely empty as of 2024 following pandemic closures and Chinese government restrictions on overseas gambling. Pub Street and the surrounding Old French Quarter contain several hundred restaurants, bars, and hotels within a six-block radius, creating density comparable to Khao San Road in Bangkok but scaled to a smaller footprint. Cambodian classical dance performances occur nightly at multiple venues, presenting episodes from the Reamker—the Khmer version of the Ramayana—with dancers trained at the Royal University of Fine Arts or private schools that revived traditions nearly destroyed when the Khmer Rouge killed an estimated 90 percent of trained artists between 1975 and 1979.