The castle was probably not completed until 1636 and shortly afterwards, in January 1642, the castle was besieged by Irish rebels. The rebels set fire to the town but failed to capture the castle. The castle seems to have survived until 1652 when it was burnt by the Earl of Clanrickard.
Manorhamilton Castle is a fortified house, a type of castle that was popular with the incoming planters into Ireland during the 17th century. It is u-shaped in plan, open to the north and with corner towers at four angles. It is surrounded by a defensive stonewall, called a bawn wall and there are the remains of towers at two corners of this wall. There is a courtyard in the space created by the u-shaped plan of the house.
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