The landscape of the Xieng Khouang plateau is dotted throughout with thousands of stone jars, in clusters from one to over a hundred jars. Initial study of the Plain of Jars by French archaeologist Madeleine Colani in the 1930's suggested that the stone jars are associated with the burial practices of the protohistoric communities living in the area. Excavation by Lao and Japanese archaeologists in the intervening years has supported this interpretation with the discovery of human remains, burial goods and ceramics dated, by comparative material from Dong Son in Viet Nam, to the Early Iron Age from approximately 500 BCE to 800 CE. Some sites contain more than 250 individual jars. The tallest jars are more than 3 meters in height and while most are undecorated, a few have carved human figures or faces. Circular stone discs found near the jars, and presumed to be lids, are also sometimes carved with representations of humans, tigers or monkeys. 

The artifacts from the Plain of Jars constitute an exceptional collection for the study of the late prehistory of mainland Southeast Asia. The jars' striking and enigmatic presence has given to the Xieng Khouang Plateau the name The Plain of Jars; little is yet known for certain about the people and culture which produced them.