Plain of Jars The Plain of Jars is a large area extending around the town of Phonsavan, where huge jars of unknown origin are scattered around the landscape. The stone jars appear in clusters, ranging from a single or a few to several hundred jars. The jars vary in height and diameter between 1 and 3 meters and are all hewn out of rock. The stone jars are undecorated with the exception of a single jar that has a human bas-relief carved on the exterior. Research of the Plain of Jars suggests that the stone jars are associated with prehistoric burial practices.