The great city of Angkor in Cambodia, first established in the ninth century, was the capital of the Khmer Empire, the major player in southeast Asia for nearly five centuries. It stretched over more than 385 square miles (1,000 square kilometers), making it the most extensive urban complex of the preindustrial world. In comparison, Philadelphia covers 135 square miles (350 sq. km), while Phoenix sprawls across more than 500 square miles (1,300 sq. km), not including the huge suburbs.
Suggested causes for the fall of the Khmer Empire in the late 14th to early 15th centuries have included war and land overexploitation. However, recent evidence suggests that prolonged droughts might have been linked to the decline of Angkor — for instance, tree rings from Vietnam suggest the region experienced long spans of drought interspersed with unusually heavy rainfall.
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