‘Y Garreg Siglo’ in Welsh, a great place to visit, not far from Pontypridd Hospital and with a marvellous view over the town. The central stone is over 5 feet high and placed there in Neolithic times. It does indeed ‘rock’ slightly back and forth if you sit or stand on it and push a bit! The stone circle surrounding it is much more recent, having been arranged there only one or two hundred years ago(there appears to be some dispute about the exact date). There are various other stones dotted about the Common. There are several places to park nearby along the road side.