In the history of Khmer architecture, Bakong stands outs as the first five-tiered temple often referred to by researchers as “Mountain Temples”. King Indravarman I inaugurated it in 881, two years after the dedication of Preah Ko temple. During that time, it was a tradition where ancient rulers undertook to erect monuments to dedicate to their ancestors first before inaugurating other structures to attribute to themselves.
You are right now standing inside the 900 x 700 m enclosure of Bakong Temple that comprises 22 brick monuments the majority of which are covered by vegetation or hidden behind residential structures. At the front section there is a 400 x 300 m moat bordered by laterite embankment. The entrance causeway of the temple is flanked by two stand-alone Naga sculptures where the tails bear the marks of Garuda claws. It was the first time in Khmer architecture where Naga figures were sculpted as stand-alone masterpieces spanning along both sides of the causeway like this.
The central tower at the uppermost tier was built at a later time, in the 12th century. There is no record of how the original tower may have looked like, unfortunately.