Bakong (Khmer:) is the first temple mountain constructed by rulers of the Khmer empire at Angkor near modern Siem Reap in Cambodia. In the final decades of the 9th century A.D, it served as the official state temple of King Indravarman I in the ancient city of Hariharalaya located in an area that today is called Roluos.

In 802 A.D., the first king of Angkor, Jayavarman II declared the sovereignty of Cambodia. Shortly thereafter, he established his capital at Hariharalaya. Late in the 9th century, his successors constructed Bakong as the first temple mountain at Angkor. In 881, King Indravarman I dedicated the temple to the god Shiva and consecrated its central religious image, a lingam whose name Sri Indresvara was a combination of the king's own and the suffix "-esvara" which stood for Shiva.

Bakong enjoyed its status as the state temple of Angkor for only a few years. Toward the end of the 9th century, Indravarman's son and successor Yasovarman I moved the capital from Hariharalaya to the area north of Siem Reap now known as Angkor Thom where he founded the new city of Yasodharapura and constructed a new temple mountain called Bakheng.

The site of Bakong measures 900 meters by 700 meters, and consists of three concentric enclosures separated by two moats. The innermost enclosure, which measures 160 meters by 120 meters, contains the central temple pyramid. Between the pyramid and the boundaries of the enclosure are eight brick temple towers, two on each side. A number of other smaller buildings are also located within the enclosure.

The pyramid itself has five levels. It is surmounted by a single tower that is much later in provenance, and the architectural style of which is not that of the 9th century foundations of Hariharalaya, but that of the 12th century temple city Angkor Wat.

Though the pyramid at one time must have been covered with bas relief carvings in stucco, today only fragments remain. A dramatic scene-fragment involving what appear to be asuras in battle gives a sense of the likely high quality of the carvings. Large stone statues of elephants are positioned as guardians at the corners of the three lower levels of the pyramid. Statues of lions guard the stairways.

Text from :

http://en.wikipedia.org/wiki/Bakong