What Is "The Plain of Jars" (Vietnam?)

In reading the history of the Vietnam War, reference is made to an area called the “Plain of Jars”? Outside of a passing reference to some ancient tombs, nothing much seems written about the rather mysterious area. Does anybody know what this is all about?

The Plain of Jars is an area in Laos with various archeological sites where they’ve unearthed a lot of stone jars. The Pathet Lao (the Laotian Communist resistance) used the area as a base during the Laotian Civil War, and so the area was fought over during the Laotian Civil War and pretty heavily bombed by the US. This has caused problems in the years since the end of the war, as there are still a lot of unexploded bombs, and getting to and working in the archeological sites is difficult.