Angkor Thom

It is a succession of cities, which took more or less final form around the end of the 12th century under the reign of Jayavarman VII, though some construction within the city walls post-dates this monarch's reign.
Recent research has confirmed the existence, up until an undetermined date, of a water course running through the city. This may well have been a branch of the O Khlot. Passing through the city on what was to become its north-south axis, the river would seem to have continued past the eastern foot of Phnom Bakheng.

Remodeling
The remodeling of urban forms which had themselves developed over the preceding 400 years was not a minor undertaking, particularly as Jayavarman sought to render the spatial composition of his city highly symbolic. In addition, the exact definition of the square resulted from a number of unavoidable constraints, such as the existence of the Phnom Bakheng.
The wall, called Jayagiri in period inscriptions, is itself surrounded by a wide moat called Jayasindhu. One inscription explicity compares this ensemble to the mountain range and sea of milk which encircle the universe in Indian cosmological conceptions adopted in ancient Cambodia.
Thus Angkor Thom was in its entirety the world created - or recreated after the city sacking by the Chams emerging as ambrosia after the Churning of the Sea of Milk. This explains why the churning episode was represented at each of the five gates giving entry to the city.
We are far from fully understanding the purely functional aspects of the city. An ancient water outlet, known as Run Tadev, is still in use today at the southwestern corner of the enclosure wall. We do not know if the nearby rectangular reservoir, Beng Thom, or the pond known as Trapeang Daun Meas in the northwestern quadrant of the Royal Palace, existed in ancient times.

A similar structure at the wall's northeastern corner is overgrown with vegetation today. Future research promises to tell us if this was another outlet or, rather, as logic suggests, a mechanism serving to introduce water into the city. Atop the wall at each of its corners, Jayavarman also erected a temple- the Prasat Chrung - along with a stela inscribed in Sanskrit. The only complete inscription, covering all four sides of the stela, is that of the southwestern Prasat Chrung.