Excavations undertaken in Houaphanh Province during the 1930s revealed the existence of ancient necropolises which are now believed to predate those of the Plain of Jars in Xieng Khouang Province. Instead of jars, these sites comprised groups of menhirs or standing stones - as many as 150 at the largest site - erected over large burial chambers covered by stone disks of up to two metres in diameter. The standing stones have been dated to 1000-500 BCE and there are about 20 such sites in Houaphanh Province. The largest and best-known of the Hintang Houamuang sites is that of San Kong Phanh, which comprises three main clusters erected along 10 kilometres of summit trails on the top of forested mountains, each cluster linked to the other by isolated groups of menhirs. The menhirs themselves take the form of long and narrow blades of cut schist erected upright in the ground, one behind the other, with the tallest often in the middle. They were erected over deep burial chambers excavated into the bedrock; access to the opening below was often through a narrow vertical chimney equipped with steps. Each of the burial chambers was covered by a large stone disc measuring up to two metres in diameter. The sites around San Kong Phanh were surveyed and partly excavated in 1931 by French archaeologist Madeleine Colani. Although finding that the burial chambers contained little but alluvial clay which had been washed into the cavities, she suggested that each was originally occupied by several individual burials, separated by the sunken blades of the schist plaques. The few artefacts recovered by the Colani expedition - including rudimentary funerary urns, ceremonial stone objects, ceramic hanging pendants and bronze bracelets - are now on display in the Lao National Museum in Vientiane. No further excavation work has been undertaken in the area since that time. Today it is believed that the people who created the menhirs of Houaphanh Province were the ancestors of those who created the Plain of Jars in Xieng Khouang Province; there is some similarity in the grave offerings, and also a similarity between the stone discs that covered the entrances to the grave shafts in Houaphanh Province and the carved lids of the jars in Xieng Khouang. It is believed that the transition from the rough upright standing stones of Houaphanh Province to the carefully hewn jars of Xieng Khouang came with the use of iron tools by about the 4th century BCE - the advent of iron forging in around the 4th century BCE offered new creative opportunities to the prehistoric necropolis builders. Local legend explains the menhirs slightly differently. An ancient people of the region called the Kha Yeui were ruled by a chief named Ba Hat, to whom the gods gave three magical objects - a double-headed drum, one face of which could be struck to make enemies disappear and the other face of which could be struck to call for help from the gods; an enormous awl which pierced the stoniest ground and made water gush out; and an axe which could cut hard rock like wood. Deciding that his people should no longer be subservient to Luang Prabang, Ba Hat angered the King of Luang Prabang, who launched an attack on the Kha Yeui. Victory went to Ba Hat, but on hearing that the King of Luang Prabang was launching a counter-attack he struck the drum to call on the gods for help. The chief of the gods immediately descended in person, but finding no enemies anywhere he punished Ba Hat for wasting his time by seizing back the magical drum. But Ba Hat still had the other two magic tools, and with his axe he and his people set about cutting blocks of stone from the Peun River valley, carrying them to the top of Sang An ridge to build the new city of Kong Phanh. Fearful of Ba Hat’s growing power, the King of Luang Prabang succeeded by a ruse in marrying his son to Ba Hat’s daughter. The prince then persuaded the Kha Yeui to place both the magic axe and the magic awl onto a white-hot brazier, where all their magic powers immediately dissappeared. So the Kha Yeui had no choice but to leave the stone blocks where they stood, and these became the menhir fields of Hintang Houamuang.