Duncannon Fort is a star shaped fortress on an important promontory in Waterford Harbour. It was built in 1588 in the expectation of an attack on the area by the Spanish Armada. The Fort is surrounded by a 30 ft high dry moat and has one of the oldest lighthouses of its kind in Ireland.

All the major buildings in the Fort surround a parade ground. A walk around the outer ramparts afford spectacular views across the estuary to Co. Waterford and down to Hook Head. Located at a lower level than the moat is the "croppy boy" cell. After the 1798 rebellion, prisoners were detained here pending transfer to Geneva Barracks for trial and sentencing. An added attraction is the Maritime Museum which charts the maritime history of one of the most dangerous coastlines in Ireland, the Wexford coast.

(Note: The name "croppy" derives from Ireland in the 1790's as a reference to people with closely cropped hair, a fashion which was associated with the anti-wig (and therefore, anti-aristocrat) French revolutionaries of the period. )