Buriram city is surrounded by a circular moat. This is one of many (hundreds?) of examples on the Khorat Plateau. The circular moats are often several kilometers in diameter and often a hundred or so meters wide. The effort to build these structures must have been rather significant. There is little information available on their date or purpose. I first noticed these structures whilst flying from Buriram to Bangkok, when I noticed many circular marks on the landscape. Sometimes surrounding a village or town. Other times aparently filled in and disused, but distinguishable from the air only, and on Google Earth.