[jsanders2001]

Makes you wonder why they abandoned those great cities?

[smokingfrog]

Some kind of pandemic most likely. Disease can spread quickly in places where population is dense, and they had no methods or knowledge to stop it.

[Redcitizen]

Mowing the grass got to be too much.

[colorado tanker]

After Angkor Wat was built the Khmers gradually converted to Buddhism. The consensus seems to be that the capital was later moved south because Angkor was too vulnerable to attack by their enemies, the Thais and Chams.

Unfortunately, except for the great temples, the Khmer built with wood, even the royal palace at Angkor. We can only turn to radar to see the monumental size of the cities, but little else is left.

FWIW, Angkor is one of the most spectacular sites I have ever visited. Definitely worth a journey.