Sprawling Remains of Ancient Cities Discovered Beneath Cambodia's Jungle

This digital terrain model of Preah Khan of Kompong Svay in Cambodia was taken using lidar. . (Photo: AngkorLidar.org)

The days of mounting an expedition to hack through a thick jungle in search of some lost city may be at an end. To discover the unknown, the rumored or the hidden is now as easy as securing a helicopter, a crew and using laser-mapping technology to peer through the thick vegetation.

For the first time, the jungle is no longer the near-impenetrable foil of archaeologists everywhere.

The latest evidence that we've entered a new age of discovery comes courtesy of an Australian team of archaeologists under the direction of Dr. Damian Evans. The team used lidar, a laser scanning technology, to survey more than 734 square miles of thick Cambodian jungle from the air. They discovered the remains of massive cities ranging in age from 900 to 1,400 years old — and all hidden beneath centuries of vegetation.

The sites are so big that at least one may be larger than Phnom Penh, the largest city in Cambodia. The most recent discoveries come after previous successes with lidar in the region, including a 2015 scan of the temple complex of Angkor Wat that revealed previously unknown buried military fortifications.

"What we had was basically a scatter of disconnected points on the map denoting temple sites. Now it's like having a detailed street map of the entire city," Evans told the AFP.

angkor lidar
An example of previously unknown features discovered using lidar at places like Banteay Chhmar and Sambor Prei Kuk in Cambodia. (Photo: AngkorLidar.org)

While lidar has been around since the 1960s, it was ineffective initially at penetrating through thick jungle canopy. The technology generates pulses of light that create a detailed image of the topography below as they bounce back. Early versions could only send out 2,000 pulses per second, which was too weak to distinguish between the leaves and branches of a tree and a structure hiding underneath. Thanks to advancements with the technology, lidar scans are now capable of firing more than 600,000 pulses per second. Sites that once took years to survey can now be documented in a few hours.

"For the first time in my 16-year career, there is no 'next big thing' – lidar is it," Evans wrote in 2013. "We have arrived. The only obvious way forward from here is to make lidar instruments cheaper, smaller, better and ubiquitous; everything else, for the time being lies firmly in the realm of science fiction."

The shift with lidar from prohibitively expensive to ubiquitous appears to coming thanks to the rise of commercial drones. Not having to rely on expensive helicopters to map a section of forest will considerably reduce the grants archaeologists need to take advantage of the technology.

"For the very first time, lidar allows us to literally shine a light into the forgotten pages of that history, and to appreciate the stories of places like Angkor in all of their awe-inspiring grandeur and complexity," added Evans.