The first castle was built on this site by Hugh Maguire in the 16th century. It featured greatly in Irish rebellions against English rule in the 16th century and was taken after an eight day siege in 1594. In 1607 it was remodelled and refurbished by Captain William Cole. The riverside tower at the south, known as the Watergate, was added at this time. In the 18th century Enniskillen castle was remodelled as the Castle Barracks.