In the 9th Century, a thriving ancient kingdom, the Khmer Empire, spread across parts of what is now modern-day Cambodia, Lao PDR, Thailand and Vietnam. The capital Angkor, which boasted up to one million residents, is thought to have been the world’s largest pre-Industrial city.
Each year, millions of tourists and travel to see its ruins. Yet as visitors marvel at the architecture of the temples, what aerial laser surveys have revealed is even more impressive: a vast urban complex of roads, canals and reservoirs. A prosperous city built on water, linked closely to the largest freshwater lake in Southeast Asia, the Tonlé Sap.
Mysteriously, in the early 15th Century the kingdom was abandoned. Many researchers now believe the collapse was climate-related, brought about by decades-long drought followed by intense flooding. Thus the element that had been central to the kingdom’s rise – water – perhaps became its downfall.