There are actually three historic sites within a very short distance of each other.
1. A neolithic burial chamber with one of those truly monstrous capstones.
2. A group of rectangular and round dwellings and comprising a walled settlement from Roman times - most of what can be seen being from the 3rd century CE.
3. Lligwy Chapel - a ruined medieval chapel built near to a vanished village. There is a most unusual burial vault.
Entry to all three is free and the sites are maintained by Cadw, the Wales equivalent of English Heritage.