Ring-forts were usually found at ground level. Another type of defensive place constructed in the Iron Age and continuing into the Middle Ages was the promontory fort. These forts were built on a spur jutting out into a sea or a lake. The Dunbeg fort on the Dingle Peninsula of Co. Kerry is the best example of this. It is now a national monument.
People can visit it, but it is very dangerous.
They were constructed with mud, timber, or stone. These were only acc essible by boat, or tortuous secret paths through marshes or under water. Castles were used as a tool to achieve military supremacy. New building methods were created in the 1100's. Twelfth century fortifications were similar to that used by the Normans.