Carrigafoyle Castle is a very fine example of 15th century building. The illustration in Pacata Hiberna shows the unique features of this castle. The castle was strongly built and ingeniously situated. Standing on the edge of the Shannon estuary on what was originally an island, Carrigafoyle Castle rises to five storeys with vaults over the second and fourth storeys. An unusually wide spiral stairs ascends in one corner of the tower which has small rooms as well as the main living spaces opening off it. The stone bawn wall at the foot of the castle contained a boat dock. One of the turrets in this wall seems to have been used as a dovecot where pigeons were kept for food.

A wide spiral staircase of 104 steps leads to the battlements and in presentation and size it rivals Blarney Castle. It rises to 26.4 meters and gives an impression of great strength. In the forefront of the view from it, Carrig Island and Scattery Island can be seen across the broad estuary of the Shannon.

Carrigafoyle Castle was the main stronghold of the O Connor Kerry, the principal chieftain of this barony named after him. For 400 years they were an important part of the ever changing political and military jigsaw of those times. From here O Connor Kerry was able to intercept ships going up the Shannon to Limerick, board them and take a part of their cargo. This practice continued until the middle of the 16th century.

In the Desmond wars in 1580, the castle came under fire from naval artillery on land and sea, under the command of Sir William Pelham. Following a two day siege the castle was breached and taken on Palm Sunday 1580. All the occupants, comprising nineteen Spanish and fifty Irish were massacred. Opposite the castle is the medieval Church of Carrigafoyle which is built in the same style as the castle.