Dunlough Castle Dunlough Castle , standing atop the cliffs at the northern tip of the Mizen Peninsula , looks at the Atlantic Ocean from the extreme southwest point of Ireland . Founded in 1207 by Donagh O ’ Mahony , Dunlough is one of the oldest Norman castle s in southern Ireland and an interesting example of Norman architecture and dry stone masonry . Physical characteristics . Dunlough Castle is a series of three fortified towers , or keep s , which stand almost invisibly upon the isthmus connecting “ Three Castles Head ” with the mainland . The only route of access is from the south , and the castle appears suddenly as you cross through the hills onto the isthmus . The towers are connected by a wall spanning more than one hundred feet from the western cliffs to the shores of an apparently man - made lake . The wall is mostly fallen today ; yet in places it stands approximately . At the eastern shore of the lake , a wall from the same period serves as a dam , preventing the lake ' s water from pouring over the cliffs into Dunmanus Bay several hundred feet below . Passage around the eastern shore of the lake is awkward ; while the castle and wall block the western shore . Only a small footpath between the westernmost ruins and the cliffs allows travelers to visit the towers and the rocky cliffs beyond . As one writer has observed , " To an invading army , the cliff ’ s edge , the defensive wall , the lake and the sternly inaccessible approach would have made the castle appear impregnable . " It is not known if Dunlough was ever attacked . History . At the time the first Norman soldiers and settlers arrived in Ireland in 1169 , the O ' Mahonys were the declining but still powerful princes of Eóganacht Raithlind , occupying approximately the area from Cork City west to Mizen Head . Their regional prominence had been diminished greatly since the MacCarthy dynasty had come south from Tipperary in the early 12th century , and faded even more rapidly as the Normans took hold of southern Ireland . Their primary Irish rivals ( and allies ) were the McCarthys and the O ' Briens . But all these groups were militarily outclassed by the Normans who followed in the wake of King Henry II ' s initial invasion . In 1177 , King Henry of England granted “ the kingdom of Cork ” to the Cambro - Norman knights Robert Fitz - Stephen and Milo de Cogan . De Cogan received the lands of west Cork , and began a push toward the Atlantic which drove regional families from the holdings in central Cork . The O ’ Mahony clan , led by their chieftain Donagh “ the Migrator , ” settled at the furthest point , the tip of the Mizen peninsula . Architecture . As an example of dry stone masonry , Dunough is unusual in that it features three towers with distinct designs , each rather smaller than the typical solitary towers of the region . Designed to fit its environment , the three keeps and the connecting wall would have been a daunting target for invading armies , though it is unknown if any ever attempted to take the castle . Each keep is three stories high , typical of rectangular towers of its day . No turrets or parapets are present among the remaining structure . The eastern keep was probably the gate tower , though the gateway itself is today in ruins . The western tower is the largest , and was most likely the residence for most of the inhabitants . Typical of " sub - towers " found in larger Norman castles , the central keep provided additional lookout and storage , and served to reinforce the strength of the connecting wall . Dunlough ' s interior design is in keeping with other early Irish castles . The presence of a spiral staircase in the eastern tower is offset by the linear staircases of the western tower , while the central tower incorporates both types of stairs . The spiral stairs of the eastern tower are today visible from the outside , due to the crumbling of the outer walls . The simple , rectangular towers of Dunlough foreshadowed the regional castles which were built in later years , many of which still stand . Plain and unornamental , these castles , many of them O ' Mahony keeps , rise from the landscape along both shores of the Mizen peninsula . A common characteristic of the O ' Mahony castles , evident at Dunlough ' s western keep , is the second - storey door . Usually directly above or just to the side of the first - storey entrance , the second - storey door was probably accessed by means of a removable wooden ladder . Inside , the door leads either forward to the second storey ( commonly wooden ) or upward through the wall to third level . The third storey at Dunlough , as at other O ' Mahony castles , is a stone floor which served as the banquet and gathering hall . This was a common feature of most Norman keeps from the early period . Dunlough ' s deterioration is attributable in part to the dry stone masonry used in its construction . This method is unusual for castles in this area , which , built in later years , made more use of wet mortar and sand . Yet the use of dry stone masonry was common in earlier Irish buildings .