Similar structures have been found throughout Northern Europe, particularly in Ireland, but none of them have the same strict and precise geometrical design of the Scandinavian ring fortresses. On the coasts of the Netherlands and Belgium there are ring castles with certain points of resemblance and on the island Walcheren there are the remnants of a castle with gateways in the four points of the compass, combined with streets. Similar forts can be found in England, such as Warham Camp. These generally date though from around the time of the Roman conquest of Celtic Britain and had been lying in ruins for hundreds of years prior to the building of the Viking ring forts.