Archaeologists have discovered a number of previously undocumented medieval cities near the ancient temple city of Angkor Wat in Cambodia.

Writing in the Journal of Archaeological Science earlier this month, Australian archaeologist Damian Evans said that cutting-edge airborne laser-scanning technology has revealed several cities between 900 and 1,400 years old beneath the tropical-forest floor; some of them rival the size of Cambodia’s capital, Phnom Penh. He claims that the recently analysed data — captured during the most extensive airborne study ever undertaken by an archaeological project, covering 734 square miles — shows that the cities would have constituted the largest empire on earth in the 12th century.

Dr Evans said that the new cities were found by an airborne laser scanner mounted on a helicopter skid pad. “The data downloaded from the ALS is used to create a 3-D model of the information captured during the flights. In order to remove tree foliage and man-made obstacles from the data, any sudden and radical changes in ground height are mapped out, with technicians fine-tuning the thresholds. Once completed, the final 3-D model is handed over to the archaeologists for analysis.”

Dr Evans said that the scanners had also identified large numbers of “mysterious geometric patterns formed from earthen embankments, which could have been gardens”.