Towards the end of the 12th century the Anglo-Normans constructed a motte-and-bailey fortification here. This was superceeded by a stone structure built in 1210, on the orders of King John of England. The Castle was built by John de Gray, Bishop of Norwich.. The 12-sided donjon dates from this time. The rest of the castle was largely destroyed during the Siege of Athlone and subsequently rebuilt and enlarged upon.