Vat Mahaphot and an ancient city are located on hilltop just south of the main town. This and other abandoned Vats in Vieng Phoukha are believed to date to the 16th – 17th centuries. Surrounding this abandoned temple is a series of ramparts called Kou Vieng in Lao. Many people believe that these ruins are protected by spirits and if you take anything from the ancient sites you will suffer sickness and perhaps death.
Source: Laos Tourism