Although for much of the period the Angkorian empire was ruled from Angkor, important secondary centres existed elsewhere. Some of these were situated in the Northern Plains, and evidence exists that these settlements helped to shape the natural landscape that exists today.
Analysis of satellite imagery and aerial photographs for the Northern Plains shows that the landscape was extensively altered by the infrastructure of the Angkorian Empire. At least four types of remains are visible: temples, roads, water bodies and agricultural systems. The Angkorian roads and temples were often associated with water sources–perhaps for religious reasons in addition to providing water for agriculture and livestock. Some of these man-made ponds (or trapeangs) are still visible and many contain permanent water. These provide a critical water supply to local people, livestock, and wildlife.
Prominent in the landscape of the Northern Plains are extensive patches of seasonally-flooded grassland, called veals. These are common in Preah Vihear Protected Forest particularly around eastern Chhep and in eastern Chaom Ksan. Signs of old agricultural systems are visible in many veals on aerial photographs. These field systems have not been used within living memory, proving that they were not built during the Khmer Rouge period. Although their origin is unknown, similar structures are found around the main settlements at Angkor and have been attributed to the Angkorian period. At least in some areas the grasslands appear in association with Angkorian trapeangs and temples.
Whilst superficially appearing to be a collection of remote agricultural villages, there is ample evidence that the landscape has been artificially enriched particularly through the construction of permanent water sources and the conversion of seasonally flooded areas into extensive grasslands. These features are concentrated around temple complexes and linked by a road network. Now abandoned, the trapeangs and veals provide critical resources for the collection of globally threatened species that is so unique to the Northern Plains.