Si Phan Don (4000 islands) is located in the south of Laos, right near the Cambodian border. Most visitors to Laos never venture this far south but it is definitely worth the effort. Hundreds of islands are scattered in the middle of the Mekong River which is up to 15km wide in this section
More info: http://www.trekearth.com/gallery/Asia/Laos/photo753012.htm
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