Recent laser surveys have revealed traces of a vast urban settlement, comparable in size to Los Angeles, around the temples of Angkor.

The ancient Khmer capital was never lost … it just got a bit overgrown

Digital terrain model of Preah Khan of Kompong Svay, east of Angkor
Digital terrain model of Preah Khan of Kompong Svay, east of Angkor © Damian Evans/Cambodian Archaeological Lidar Initiative - The Khmer’s mastery over the natural landscape was perhaps their greatest achievement, and the lidar mapping has exposed complex levels of terraforming and water management systems that were way ahead of any other settlement of the era.Once again, earlier archaeological studies focused on the symbolic role of water in Angkor’s cosmological order, reading the vast reservoirs as symbols of the mythological oceans surrounding Mount Meru, home of the Hindu gods. While the watercourses evidently played a part in the sacred geography of the city, they were fundamentally there to irrigate the rice fields, the source of the empire’s great wealth. Success in a tropical climate ultimately depended on the ability to mitigate flooding during the summer monsoon and store enough water to irrigate the fields during dry season – something the Khmer rulers had clearly mastered.Residential neighbourhoods were arranged around thousands of communal rainfall ponds, while the fields were irrigated by a pair of great reservoirs, or “barays”, the whole system connected by an extensive network of canals and channels. The West Baray, which stretches five miles by one mile to the west of downtown Angkor, remains the largest hand-cut body of water on earth. Contained by tall earthen dikes, it stands as the pinnacle of the Khmer ability to harness the landscape for its own ends.

When you’re exploring the enigmatic temples of Angkor, along with the two million other tourists who come here each year, it can still feel like you’re uncovering this lost kingdom for the first time. What’s harder to imagine as you roam between the ruined sites, each set apart in the depths of the jungle, is that these monuments were once part of the largest, most sprawling city on the planet.

It’s a hunch that archaeologists have had for decades, but which was only recently confirmed in astonishing detail by an aerial laser survey, which cut through the foliage for the first time a few years ago to reveal the grid of a vast urban settlement stretching for miles around the moated compounds. It showed that the ancient Khmer capital, which flourished from the ninth to 15th centuries, had more in common with Los Angeles than this series of temples standing in splendid isolation in the jungle might suggest.

“The laser technology has been a total game-changer,” says Damian Evans, the Australian archaeologist who has been leading the airborne scanning survey at the École Française d’Extrême-Orient, working with Cambodian APSARA National Authority and the Ministry of Culture and Fine Arts. “Our surveys have revealed the pattern of a settlement comparable in size to LA or Sydney, with an urban form that resembles the kind of dispersed low-density megacity characteristic of the modern world.”

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Thanks to technology developed by Nasa, all of this could be gleaned from a few hours of helicopter flight, as opposed to generations of hacking through the undergrowth with machetes (while keeping a lookout for landmines). Shooting a million laser beams every four seconds from the bottom of a helicopter, the lidar technology (which stands for light imaging detection and ranging) allows a kind of virtual deforestation to take place, stripping away the tree canopy to reveal what lies beneath on the forest floor.

The findings were a revelation. The scanning exposed a topography inscribed with a precise network of furrows and mounds, the bones of the city etched into the landscape.

“On the ground you just see lumps and bumps,” says Evans, “but this aerial view shows a very sophisticated system of road networks, planned neighbourhoods and intricate waterworks. Angkor was a work of geoengineering on an unparalleled scale.”

Any evidence of these neighbourhoods on the ground has long since rotted away. In Khmer society, stone was reserved exclusively for religious monuments, built of great blocks floated here from quarries 30 miles away along specially dug canals (as the wider laser survey revealed last year). Everything else – even the royal palaces – was made of wood and thatch, with homes raised up on stilts on top of earthen mounds, designed to keep them above the floodwaters in the rainy season.

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