The June 13 issue of the Journal of Archaeological Science features the discovery of entire previously undiscovered cities lying beneath the earth's surface, lost to humanity until aerial laser scanning revealed their secrets. The discoveries also showcase how sophisticated lidar technology can be applied.

Lidar is an optical sensing mechanism used in applications as diverse as agriculture, self-driving cars, law enforcement – in the form of next-generation radar guns – and even the 3D scanning used in a Radiohead music video. It works by using a rapidly pulsing light beam that relies on gallium-aluminium-arsenide laser (GaAlAs) diodes, or other semiconductor combinations, to create digital maps, surveying images and real-time navigational tools in 3D. Lidar technology was used on the Mars Polar Lander to create images by measuring the behavior of the light beams, and that's exactly how it worked at Angkor Wat.

The Cambodian Archaeological Lidar Initiative (CALI) project, funded by the European Research Council and led by principal investigator Damian Evans at the École française d'Extrême-Orient, revealed secrets lost for centuries. Roads, canals, gardens and city structures came to life, putting 12^th-century Khmer people and urban life at the center of understanding. The aerial lidar research results are that dramatic.

"It is as if a bright light has been switched on to illuminate the previous dark veil that covered these great sites," said Charles Higham of the University of Otago in New Zealand, in a Guardian interview with the pre-eminent scholar on southeast Asia. "Personally, it is wonderful to be alive as these new discoveries are being made. Emotionally, I am stunned. Intellectually, I am stimulated." His colleagues are no less impressed, and call the discoveries game-changing, revolutionary and a rewrite of history.

Scientists say that the use of lidar at Angkor Wat results in the single greatest advance in understanding Angkorian civilization in the last 50 to 100 years. The project represents the most extensive use of lidar to date for archaeological purposes, but the paradox is that the cutting edge technology of the 21^st century is filling in the contours of a culture whose own advances – earthen works, wooden and thatch structures, for example – were unable to tell their own story because of fragility and impermanence.

Now, the social and cultural clues of a people whose decline and disappearance has always remained a mystery are vivid and alive. Insights about agriculture and industry, water systems and transportation, religion and daily life emerge at levels of detail that track to the household and neighborhood level. In the bigger picture, the CALI team and their lidar results create an advanced understanding of threats and resilience in ancient civilizations. Their research helps us to more precisely evaluate the changes in our own environment, and develop regional sustainability models for today that are rooted in our past.