The keep is roughly thirty feet square and was once of four storeys. The corners of the tower have been much rebuilt, probably due to insecure foundations. The entire south-east corner of the tower has been replaced and it is possible that when first constructed there was a spiral stair here to allow access to the upper floors. During the twelfth century the powerful curtain wall with gate was added to the rampart around the site. This gateway is one of the finest carved castle gateways in Wales and is comparable with the much more ornate work at Newcastle Bridgend castle. The two gates hanging within the gateway, although of different ages, would appear to be very old – the gates at Chepstow have been dendrochronologically dated to the reign of Henry II (1154-89). Probably during the troubles of the Barons’ War a small gatehouse was added in front of the gateway to make a proper gatehouse complete with portcullis. The portcullis mechanism mounted on the wall walk was reached via a flight of steps up over the back of the gate passageway which also allowed access to the wall walks.