From the 9th to 13th centuries A.D., a dozen Khmer kings built successive capitals on a fertile plain between the Kulen Hills and the Tonle Sap Lake in northern Cambodia. With a sophisticated irrigation system, the Khmer civilisation was able to produce sufficient rice for a million inhabitants, and construct a multitude of monuments in laterite, brick and sandstone. What factors contributed to the decline of this 'Angkor empire', and did problems of water management weaken it substantially? Dr Heng Thung, a geologist who has been studying aerial photographs and satellite imagery, provides compelling intepretations from the perspectives of hydrology, geology and topography
