Pre-Angkor temples generally consisted of one single square brick sanctuary which housed the divinity to which the temple was devoted.
In Angkor times the number of sanctuaries multiplied, and by the end of the 12th century CE, under the reign of Jayavarman VII, temples had become complex structures where hundreds deities were worshipped.
The prasat (sanctuary) tower was built around a square cella, a room housing either the statue of a divinity or, most often in Angkor, a linga, the symbolic representation of Shiva. The cella was small. It was not meant to accommodate a congregation, but rather just the high priests and perhaps sometimes the king and a few of his selected dignitaries.
The sanctuary’s tower usually had five receding levels (their size was progressively reduced). Four of these levels were a replica of the sanctuary’s first Ievel, and the fifth level was in the shape of a lotus flower, which sometimes contained a sacred deposit, such as at Banteay Srei.
A great example of a sanctuary can be seen in my work Bakong I, Angkor, Cambodia. 2018.