The Plain of Jars is a collection of sites near Phonsavan containing thousands of stone jars, which lie scattered throughout the Xieng Khouang plain. Archaeologists believe that the jars were used 1,500 to 2,000 years ago, by an ancient Southeast Asian race whose culture is now totally unknown. The jars may have been used as funeral urns or perhaps storage for food. The Plain of Jars is perhaps the most dangerous archaeological area in the world due to the large number of unexploded bombs left behind by America's so-called Secret War in Laos in the 1960s.