The Khmer Empire: Angkor Wat and the World's Largest Religious Site

The Largest City on Earth Before the Industrial Age

At its height in the 12th century CE, the Khmer capital of Angkor covered approximately 1,000 square kilometers and supported an estimated population of 750,000 to 1 million people — making it the largest urban complex in the pre-industrial world. Greater London in 1800 had approximately 1 million people spread across a much smaller area. Angkor sustained this population through a system of hydraulic engineering — reservoirs, canals, and moats — that captured monsoon rains and distributed water through the dry season. The Angkor Wat temple complex, built at the center of this civilization, remains the largest religious monument ever constructed, covering approximately 162 hectares.

Origins: The Foundation of the Khmer State

The Khmer Empire traces its founding to King Jayavarman II, who unified a fragmented Cambodian polity around 802 CE and established the concept of the devaraja (god-king), asserting divine authority tied to the Hindu god Shiva. His capital moved several times, eventually settling in the Angkor region of northwest Cambodia. The empire's location on the Mekong River and near the Tonle Sap lake — Southeast Asia's largest freshwater lake, which floods dramatically each monsoon season — provided agricultural abundance that financed extraordinary construction projects.

• Jayavarman II: founder, unified the Khmer state ca. 802 CE
• Empire controlled territory encompassing modern Cambodia, Laos, Thailand, and parts of Vietnam and Myanmar at its greatest extent
• Hindu and later Buddhist religious traditions shaped art, architecture, and statecraft
• Sanskrit and Old Khmer were administrative and religious languages
• Economy based on rice agriculture, enabled by elaborate water management infrastructure

Angkor Wat: Construction and Symbolism

Angkor Wat was built by King Suryavarman II (r. 1113–1150 CE) and dedicated to the Hindu god Vishnu. Unlike most Khmer temples oriented to the east, Angkor Wat faces west — associated with the setting sun and death in Hindu cosmology, suggesting it served in part as a funerary monument for its builder. The temple's five towers represent Mount Meru, the cosmic mountain at the center of Hindu and Buddhist cosmology. The outer moat, 190 meters wide and 5.5 kilometers in circumference, represents the mythological ocean surrounding Mount Meru.

Jayavarman VII and the Buddhist Transformation

The greatest builder of the Khmer Empire was Jayavarman VII (r. 1181–1218 CE), who converted the empire from Hinduism to Mahayana Buddhism after repelling a devastating Cham invasion in 1177. He built more temples, roads, hospitals, and public works than any other Khmer ruler. His projects included the Bayon temple (famous for its 216 carved faces), the Ta Prohm monastery, Preah Khan, and over 100 hospitals distributed throughout the empire. Inscriptions from his reign describe a network of 102 hospitals serving the population.

• Bayon temple features 54 towers with 216 carved faces believed to represent Jayavarman VII as bodhisattva Avalokiteshvara
• Ta Prohm was built as a monastery and university — inscriptions record 12,640 people living there, including 18 high priests and 615 female dancers
• Royal road network connected Angkor to the empire's provinces, with 121 rest houses documented
• Jayavarman VII is regarded as the greatest Khmer king and deeply venerated in Cambodia today

The Hydraulic City

Angkor's ability to sustain its enormous population rested on water management technology of extraordinary sophistication. The city's engineers built two massive reservoirs (barays): the West Baray (8 km × 2.1 km, capacity ~50 million cubic meters) and the East Baray (7 km × 1.8 km). A network of channels, moats, and smaller ponds regulated the flow from these reservoirs through the agricultural hinterland.

Water is everything. Always was.

LiDAR (Light Detection and Ranging) surveys conducted from 2012 onward revealed the full extent of Angkor's water infrastructure, showing a hydraulic network far more complex and extensive than previously understood, with canals and embankments spanning the entire metropolitan area.

Decline of the Khmer Empire

The Khmer Empire entered prolonged decline after the 13th century. The causes are multiple and interrelated.

Rediscovery and Archaeological Legacy

Angkor was never entirely forgotten by Cambodians, but the site was largely unknown to the outside world until French naturalist Henri Mouhot published accounts of his visits in 1860. The École française d'Extrême-Orient (EFEO) began systematic mapping and restoration from 1908 onward. A UNESCO World Heritage Site since 1992, Angkor Wat receives approximately 2–3 million visitors annually, making it one of Southeast Asia's most visited cultural sites. Ongoing LiDAR surveys continue to reveal previously unknown infrastructure beneath the jungle canopy, expanding understanding of one of history's most impressive pre-modern urban civilizations.