PC Esther Davies, of Dyfed-Powys Police's rural crime team, said: "We are saddened by the vandalism to the Pentre Ifan burial chamber. "This is one of the most famous prehistoric sites in Wales ...

The oldest buildings in the world have existed for thousands of years and some are still in use. Their remains are used to study human history and heritage.

There were also smaller graves, with a single burial chamber. A Neolithic grave at Pentre Ifan, Wales. When it was built, the stones would have been covered by a large mound of earth.