Jars More than 120 jar sites have been identified in
Xiangkhouang Province and surrounding areas, with 129 sites now confirmed by recent surveys. Today, UNESCO officially recognizes over 50 sites, but there are additional documented sites not officially recognized. Each site has between one and 400 stone jars. Documented sites now include over 2,100 jars. The jars vary in height and diameter between 1 m and 3 m and are all
hewn from rock. Their shape is cylindrical, with the bottom always wider than the top. Stone discs were also found. The discs differ from the lids, as they have at least one flat side. Previous theories that the discs could have been lids were disproved due to that none of the discs were found on top of a jar and none would fit on the tops of the jars. Fewer discs have been found than jars, totaling 200 discs. It is possible that the discs may have been used as burial markers, as the discs were found nearby jars or could have been placed on the ground to mark a burial pit. These later excavations revealed that multiple individuals were interred in shared mortuary contexts. No further archaeological research was conducted until November 1994, when Professor Eiji Nitta of
Kagoshima University and Lao archaeologist Thongsa Sayavongkhamdy surveyed and mapped Site 1. Nitta claimed that the surrounding burial pits were contemporaneous to the jars, as they were cut into the surface on which the jars had been placed. Nitta believed the jars were symbolic monuments to mark the surrounding burials. He dated the Plain of Jars to the late second or early first millennium BC based on the burial urn and associated
grave goods. Sayavongkhamdy undertook surveys and excavations between 1994 and 1996, supported by the
Australian National University. Sayavongkhamdy and
Peter Bellwood interpreted the stone jars as a central person's primary or secondary burial, surrounded by secondary burials of family members. Archaeological data collected during bomb clearance operations supervised by
UNESCO archaeologist Julie Van Den Bergh in 2004–2005 and again in 2007 provided similar archaeological results. Like Nitta, Van Den Bergh concluded that the jars and surrounding burials were contemporaneous. Archaeological research conducted by Dougald O'Reilly, et al. in 2018 that covered 59 sites under the Safeguarding the Plain of Jars Project, or the SPJP's, report and dozens of undocumented and possible sites, revealed that jar sites were typically built in mountainous areas and most don't have many jars, with 16 sites having between 20-60 jars and only three sites with over 200 jars. Quarry sites, such as those near Jar Sites 2 and 3, contain partially hewn jars still embedded in the bedrock, providing clear evidence of on-site extraction and initial shaping. Regional differences in jar shape have been noted. While the differences in most cases can be attributed to choice and manipulation of rock source, some differences in form (such as variations in the placement of jar apertures) appear to be unique to specific sites. The majority of the jars are sandstone. The largest jars are made of sandstone and they are not found in plains or lowland areas. These large sandstone jars may only be found in more mountainous areas due to the more intensive techniques in quarrying and moving that were required for large jars, as opposed to small jars. A mountainous location would also allow for a close proximity to quarries. Analysis of detrital zircon from jars at Site 1 indicates the stone was transported from a quarry approximately 8 kilometers away. Granite jars have only been found in one province, the Khun District, and are often found with a high degree of weathering. Many of the granite jars found have been very small, this might be due to the higher amount of time and effort required for cutting blocks from a granite rock mass. Conglomerate jars are composed of a combination "medium gravel to cobble sized clasts set in a fine matrix," resulting in jars that are often found in very fragmented and poor condition. Limestone jars have been found in two types: a weaker and a stronger variation. The weaker, honeycombed, brittle limestone exhibited more signs of weathering and were found in poor condition. The stronger, mid grey, reef limestone with fine-scale bedding exhibited less signs of weathering, but were still not found in the best condition. Not many sites have limestone jars, as they are only found at Site 39 (Ban Phonekham), Ban Tha, Site 41 (Phou En Kha), and Site 43 (Phu Hai Hin). There is only one site where breccia jars are found: Ban Nom Hom. The site is located on a large-scale fault that resulted in a steep sided valley and hot springs found locally in the area that effected the composition and the separation of jars at the site. Two principal
iron ore deposits exist in Laos, both in Xiangkhouang. The presence and locations of the numerous jar sites in Xiangkhouang may relate to trading and mining activities. History has shown that Xiangkhouang, at the northern end of the
Annamite Range, provides relative easy passage from the north and east to the south and west. Within the geographic setting of Xiangkhouang, the jar sites may reflect a network of intercultural villages, whereby the locations of the jars are associated with long-distance overland routes which connect the
Mekong basin and the
Gulf of Tonkin System. The jar sites show superficial regional differences, such as jar form, material, and the number of jars per site, but all share common setting characteristics such as burial practices, elevated locations, and commanding views over the surrounding area.
Mortuary ritual Human remains have been found at many of the Plain of Jars sites. Remains have been found both inside of and in secondary burials nearby jars. At Site 1, human remains were found in several stone jars and burial pits, occasionally underneath stone slabs. During an excavation in 2004 led by Van Den Burg, human remains were also found in two ceramic vessels. Later excavation in 2016 hoped to recover DNA from human remains found at Site 1 in order to find out the ethnicity of the people buried there. They also hoped to accurately date the remains, as there has been much difficultly in dating remains at the Plain of Jars due to many of the dates relating to the sites' jars, not the remains. However, their findings were not documented. Later bomb clearance operations did not involve emptying the jars and thus no additional evidence could be gathered, Van Den Bergh suggested that the stone jars initially may have been used to distill the dead bodies and that the cremated remains within the jars represent the most recent phase in the Plain of Jars. The jars with smaller apertures may reflect the diminishing need to place an entire body inside. It was also suggested that the jars, as in traditional Southeast Asian royal mortuary practices, functioned as "distilling vessels", by R. Engelhardt and P. Rogers in 2001. In contemporary funerary practices followed by Thai, Cambodian, and Lao royalty, the corpse of the deceased is placed into an urn during the early stages of the funeral rites, at which time the soul of deceased is believed to be undergoing gradual transformation from the earthly to the spiritual world. The ritual decomposition is later followed by cremation and secondary burial. The royal burials are across watercourses from the habitation areas in a geographically high, prominent area. Among the
Black Thai people who have been in the region at least since the 11th century, the upper classes are cremated in the belief that it will release their spirits to heaven, while commoners are buried, leaving their spirits to remain on Earth. Many of the human remains found at the Plain of Jars were cremated. Variations in the practices of cremation inside jars and secondary burials outside jars, as noted by Colani, have proven difficult to explain. The cremated remains seem to mainly belong to adolescents. A cave at Site 1 is a natural limestone formation with an opening to the northwest and two man-made holes at the top. These holes are thought to have been chimneys for a crematorium. Colani excavated inside the cave in the early 1930s and found material to support a crematorium theory. ==Hierarchies within==