National Geographic recently featured an article by Richard Stone on the Angkor and the Khmer Empire.
[…Angkor is the scene of one of the greatest vanishing acts of all time. The Khmer kingdom lasted from the 9th to the 15th centuries, and at its height dominated a wide swath of Southeast Asia, from Myanmar (Burma) in the west to Vietnam in the east. As many as 750,000 people lived in Angkor, its capital, which sprawled across an area the size of New York City’s five boroughs, making it the most extensive urban complex of the preindustrial world. By the late 16th century, when Portuguese missionaries came upon the lotus-shaped towers of Angkor Wat—the most elaborate of the city’s temples and the world’s largest religious monument—the once resplendent capital of the empire was in its death throes…]
The article is accompanied by the set of excellent interactive sequences depicting the temples of Angkor, Khmer timeline and 3D animations.