aernarfon Castle was built by King Edward I and his master castle builder, James of St George, who started work on the new castle in around 1283. The site was previously occupied by a Norman Motte and Bailey castle and before that a Roman fort. The castle walls are dominated by thirteen polygonal towers, some large and some small. Normally the towers in the castles constructed at the time were circular. The motte was not removed by Edward and was incorporated into the eastern section of the castle although it has been removed since. The castle is elongated in the east-west direction, with the main entrance on the northern side protected by two of the towers and known as the King's Gate. This entrance would have been defended by up to six portcullises and if the castle had been finished would have led to a large octagonal area that would have provided access to the east and west sections of the rest of the castle. Two of the towers are large enough to be thought of as keep-towers and both are in the eastern section of the castle. The Eagle tower is positioned so that it can be resupplied by sea and could be used as a place of safety even if the rest of the castle had been captured.