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.
I think the stone structures were erected (as was done in Venice) on logs pounded down into the soft ground. And the first four burned down, fell over, and then sank into the swamp. ;’)