Archaeology magazine (July/August 2005) has an article on the Plain of Jars, in northern Laos.

(Article by Karen J. Coates, pp 30-35.)

These huge "jars" carved into rocks are scattered around northern Laos, in the Xieng Khouang province, a hazardous place to travel due to much more modern land mines still in place.

Archaeologists consider these to be mortuary objects, as human remains have been discovered in many. Most are sandstone, some are granite, and the tallest known one stands 9 feet. They come in a couple different shapes, and at least some apparently had lids. Over two thousand have been identified.

The article poses questions about the purpose and meanings of these jars. It is unknown how old they are, but guesses range to about two thousand years. Right now, the extensive site is being surveyed for inclusion as a World Heritage site, which means research is more about cataloging than analysis or excavations.

One local legend holds that the jars held rice whiskey (lao lao) to celebrate the triumph at the end of an ancient epic battle.

There's some great photography and further information, plus the bounty of questions being asked, in the article. Worth picking the magazine up.