The ruins of many ancient Khmer stone monuments and the ancient cities of Sema and Korat (aka Nakhon Raj or Khorakha Pura) are located about 30 kilometers west of Korat near Sung Noen. The ancient cities were abandoned with the fall of the Khmer empire and were consolidated and moved to present day Nakhon Ratchasima by King Narai in the 17th century.
Prasat Non Ku
Prasat Muang Khaek
Prasat Muang Kao
Not much is left of the ancient city of Sema. Just a few ruins, as above.
And this ancient canal at Muang Sema