Indravarman I builds the Indratataka, Preah Ko and the Bakong

Indravarman, who came to the throne in 877 and was apparently not related to his two predecessors, resumed the tradition of royal inscriptions after the silence of Jayavarman II and III. In the first year of his reign, according to George Coedès, he began the Indratataka north of the capital; an inscription preserves his vow that in five days he would begin digging. About 3.8 by 0.8 kilometres, it was larger than any earlier Khmer reservoir and stored water for the dry season — the first of the great barays that the kings of Angkor built on an ever larger scale, both for irrigation and as images of the ocean around the cosmic mountain.

In 879/880 (Shaka 801) he dedicated the six stuccoed brick towers of Preah Ko to statues of his parents, his maternal grandparents and Jayavarman II and his queen, deified in the forms of Shiva and his consort. In 881 he inaugurated the Bakong, a sandstone pyramid of five terraces amid moats and enclosures, for the royal linga Indreshvara, whose name joined his own with that of Shiva; its causeway has the earliest naga balustrades of Khmer architecture, and some scholars see the Borobudur of Java as its model. The temple-mountain at the centre of the royal city became the pattern for his successors; his son Yashovarman I added the temple of Lolei on an island in the Indratataka and then moved the capital to Yashodharapura at Angkor.