Bomb Shells and the Plain of Jars

From Luang Prabang I traveled east on a local bus for 8 hours to the town of Phonsovan in the Laotian highlands. Eastern Laos was heavily bombed by the US in the Vietnam war in an attempt to stop the Viet Cong spreading their influence, and there are reminders of this everywhere - you are warned everywhere to stay strictly to footpaths to avoid unexploded bombs and at the guest house I stayed in the fire (its cold in the highlands at night) was made out of a used bomb shell! Other than war fragments, the main sights to see in the area are the surreal Plain of Jars (over three sites), which are collections of large stone jars over 1,500 years. However, no-one really knows what their purpose was?