The Khmer term "Chrung" (pronounced "tshrong") means "corner" or "angle". That's the name of the location, the four corners of the city walls of Angkor Thom. Thus, Prasat Chrung is not one temple, but four, and they are in more than three kilometres distance from each other. Nevertheless, the shared name makes sense as the temples are similar in design, too. All of them are simple Prasat towers on a cruciform ground plan and open to the east, the two Prasat Chrungs on the eastern city wall have additional entrances to the west. The walls are decorated in the Bayon style of Angkor Thom, for example with female divine beings called Devatas in niches. Pediments show standing Avalokiteshvaras, but many of them defaced or scratched out during the reign of the Hindu iconoclast Jayavarman VIII. A square pavilion sheltered an inscription stele.
The southeastern Prasat Chrung is the best preserved of the four strcuctures. Besides, it was the only one with the stele containing the complete original inscription in Sanskrit on all four sides of the slab, today is housed in the Conservation office. The Prasat Chrung inscription not only mentions the foundation of Angkor Thom, but the previous history of Angkor as well. It is the record from which most books about Khmer history took the information that Angkor Wat builder Suryavarman II came to power by personally killing his great-uncle Dharanindravarman in combat, though this is not mentioned on the more contemporary Khmer inscriptions at Wat Po (Wat Phu) and Bau That in southern Laos.
The Prasat Chrung temples were dedicated to the Bodhisattva Lokeshvara (Avalokiteshvara), the same Mahayana saviour to whom the central Bayon temple of Angkor Thom was dedicated. So they belong to an integral masterplan of Angkor Thom, which was not only a city, but a gigantic Mahayana Buddhist temple compound.
Near the southwestern Prasat Chrung, the sewage of Angkor Thom was collected in Beng Thom ("Pond Big"), from where it poured out of the city through five corbelled arches under the city wall, the huge outlet is called Run Tadev.
A visit of a Prasat Chrung temple requires a 1.5 km walk or bicycle ride on the city walls, 3 km up and down, this is why Prasat Chrung is untouristed and pretty charming. The corner locations additionally offer great views to the city moat of Angkor Thom. In case you have time enough, it's definitely worth a visit. Exploring the city ramparts of Angkor Thom completely, requires a 12 kilometre journey, the track between Angkor Thom's North gate and the North-East Prasat Chrung is the most difficult one for hikers and bikers.
The most interesting of the four Prasat Chrung locations is at the southeastern corner of Angkor Thom, as already mentioned. There is no optimal time for visiting it. Your ticket will not be checked at any of the four Prasat Chrungs, but you should have one when walking through Angkor Thom.