One of the challenges to understanding Angkor is that there are very few written accounts of the empire at its peak. There are some court records and inscriptions, which help to place things in historical context, but there's very little about the daily life of the city, the court, or the people themselves. Of the few accounts that have come down to us, perhaps the most complete is the memoirs of the Chinese diplomat Zhou Daguan.
Zhou Daguan was in Angkor for just one full year, from August 1296 until July 1297. Some time after his return, he wrote a detailed account of his time at the capital of the Khmer empire. From him, we have detailed descriptions of what Angkor Thom and the royal palace really looked like, as well as glimpses into the everyday life of the common people.