Annalee Newitz has a great article in Ars Technica that reviews a bunch of recnet archaeological work on the urban complex of Angkor Wat: “How archaeologists found the lost medieval megacity of Angkor”. This is one of several cases in which archaeologists are using large-scale LIDAR survey to learn more about the development and later abandonment of cities.
Archaeological researcher Piphal Heng, who studies Cambodian settlement history, told Ars that the LiDAR maps peeled back the forest canopy to reveal meticulous grids of highways and low-density neighborhoods of thousands of houses and pools of water. There was "a complex urban grid system that extended outside the walls of Angkor Thom and other large temple complexes such as Angkor Wat, Preah Khan, and Ta Prohm," he said. With the new data, scientists had solid evidence that the city of Angkor sprawled over an area of at least 40 to 50 square km. It was home to almost a million people. The scattered, moated complexes like Angkor Wat and Angkor Thom were merely the most enduring features of what we now know was the biggest city on Earth during the 12th and 13th centuries.
The famous, densely occupied city centers of such places, with their large temples and other civic structures, have obviously occupied a lot of attention from archaeologists in the past. However, focusing on these obvious structures gives a misleading picture of how the urban centers were maintained by the much larger population living at lower density over the surrounding area.
These good surveys from LIDAR and other data sources enable archaeologists to understand what they are sampling when they look at surrounding areas. They can focus excavation work on particular neighborhoods within the broader urban area, finding out whether they are diverse and understanding their economic basis:
The picture that's emerging of Angkor is much like a modern low-density city with mixed use residential and farm areas. As Evans put it to Ars, "in the densely inhabited downtown core there are no fields, but that nice, formally planned city center gradually gives way to an extended agro-urban hinterland where neighborhoods are intermingled with rice-growing areas, and there is no clear distinction between what is 'urban' or 'rural'." The city was a miracle of geoengineering with every acre transformed by human hands, whether for agriculture or architecture.
It’s pretty cool to find evidence of engineered landscapes extending out far beyond the massive structures. Geoengineering was a much greater accomplishment in many ancient societies than any of the large temple or funerary complexes that they created.