A major archaeological wonder, the Plain of Jars is one of the world's most tantalizing mysteries. The broad, mountain-ringed plain northeast of Vientiane is littered with hundreds of ancient stone and clay jars, some estimated to weigh 5 or 6 tons. The jars are said to be at least 2,000 years old, but no one knows who made them or why. They survived heavy bombing during the Vietnam War, and their sheer size has kept them out of the hands of antiquities hunters.
The jars are scattered over three main areas, but only the Ban Ang site is accessible and worth visiting. Here you can find some 300 jars dotting a windswept plateau about 12 km (7½ miles) from Phonsavan, the capital of Xieng Khuang Province. This is true Hmong territory: you pass Hmong villages on the way from Phonsavan to Ban Ang and on Highway 7, which leads east to the Vietnamese border at Nong Het. There's much of interest in this remote area along Highway 7, including hot mineral springs at Muang Kham. From Muang Kham, a road leads to Vieng Xay, which has more than 100 limestone caves, some of them used as hideouts by the revolutionary Pathet Lao during the war years.