Photo ©Malcolm Butler

It is thought that construction started around the end of the 12th century. Initially it consisted of a central square stone keep but by 1313 the original keep had been reinforced with towers to the west and south. In the 14th century an east tower, gatehouses, and curtain wall were added by successive rulers of Mann. During the Civil War the castle was held for the King and was the last stronghold of the Royalist cause until it surrendered to Parliamentarian forces in October 1651. The keep was converted into a prison between 1813 - 1827, when the present Court House was made into the Outer Gatehouse, until 1891 when it was moved to Douglas.

It is now run as a museum by Manx National Heritage.