Built in the mid-11th century, it is a three-tiered temple mountain built as the state temple of Udayadityavarman II dedicated to the Hindu God Shiva. It is the archetype of the Baphuon style. The temple adjoins the southern enclosure of the royal palace and measures 120 metres east-west by 100 metres north-south at its base and stands 34 meters tall without its tower, which would have made it roughly 50 meters tall. Its appearance apparently impressed Temür Khan's late 13th century envoy Chou Ta-kuan during his visit from 1296 to 1297, who said it was 'the Tower of Bronze...a truly astonishing spectacle, with more than ten chambers at its base.' In the late 15th century, the Baphuon was converted to a Buddhist temple.
A 9 meter tall by 70 meter long statue of a reclining Buddha was built on the west side's second level, which probably required the demolition of the 8 meter tower above, thus explaining its current absence. The temple was built on land filled with sand, and due to its immense size the site was unstable throughout its history. Large portions had probably already collapsed by the time the Buddha was added.