Bakong was the earliest of the great Khmer temples, completed in 881 during the reign of Indravarman I at the capital of Hariharalya. The structure of Bakong took shape of stepped pyramid, popularly identified as temple mountain of early Khmer temple architecture. The striking similarity of the Bakong and Borobudur temple in Java. Bakong represents the first application of the temple-mountain architectural formula on a grand scale and set the architectural tone for the next 400 years. The temple displays a very early use of stone rather than brick.
The layout of the temple is conceived as a five-tiered pyramid with the central sanctuary, dedicated to Shiva, facing east. Twelve small towers are placed around the central sanctuary on the fourth tier of the pyramid. The base of the temple is surrounded by a further 8 towers--two to each side--which are in turn surrounded by a rectangular enclosure with four gopuras (one on each side). Beyond this ensemble was a set of two moats and and an additional enclosure, bringing the total size of the temple complex to 900 x 700 meters.