Archaeologists in Cambodia have found multiple, previously undocumented medieval cities not far from the ancient temple city of Angkor Wat. The Australian archaeologist Dr Damian Evans ... will announce that cutting-edge airborne laser scanning technology has revealed multiple cities between 900 and 1,400 years old beneath the tropical forest floor, some of which rival the size of Cambodia's capital, Phnom Penh. Some experts believe that the recently analysed data - captured in 2015 during the most extensive airborne study ever undertaken by an archaeological project, covering 734 sq miles (1,901 sq km) - shows that the colossal, densely populated cities would have constituted the largest empire on earth at the time of its peak in the 12th century. Evans said: We have entire cities discovered beneath the forest that no one knew were there." [A prior] survey uncovered an array of discoveries, including elaborate water systems that were built hundreds of years before historians believed the technology existed. The [latest] findings are expected to challenge theories on how the Khmer empire developed, dominated the region, and declined around the 15th century. "Our coverage of the post-Angkorian capitals also provides ... new insights on the 'collapse' of Angkor," Evans said. "There's an idea that somehow the Thais invaded and everyone fled down south - that didn't happen. It calls into question the whole notion of an Angkorian collapse."