Staigue Stone Fort

"Staigue stone fort is a partly ruined round stone fort, located three miles west of Sneem, on the Iveragh peninsula, County Kerry, Ireland. Dating is difficult, but the fort is thought to have been built during the late iron age, probably somewhere between 300 and 400 AD, as a defensive stronghold for a local lord or king. The fort's walls are up to 5.5m (18ft) high in places, 4m (13ft) thick and 27.4m (90ft) in diameter. The interior is reached through a 1.8m passage roofed with double lintels. The fort is surrounded by a large bank and ditch, to be seen on the north side. Staigue Fort represents a considerable feat in engineering and construction. It was built without use of mortar, using undressed stones. There is evidence that copper was excavated in the surrounding area and appears to be a place of worship, an observatory and a place of defence." -Wikipedia