Mysterious giant stone jars of unknown ancient origin are scattered over hundreds of hilly square kilometres around Phonsavan, giving the area the misleading name of Plain of Jars (ທົ່ງໄຫຫິນ). Remarkably, little is known about the Austro-Asiatic civilisation that created them, although archaeologists estimate they date from the Southeast Asian iron age (500 BC to AD 200) and were likely used for elaborate burial rituals.

Smaller jars have long since been carted off by collectors but around 2500 larger jars, jar fragments and 'lids' remain. As the region was carpet-bombed throughout the Indochina wars, it's miraculous that so many artefacts survived. Only nine of the 90 recorded jar sites have so far been cleared of unexploded ordnance (UXO), and then only within relatively limited areas. These sites, and their access paths, are delineated by easily missed red-and-white marker stones: remain vigilant.

Sites 1, 2 and 3 form the bases of most tour loops.