Dún Aonghasa, also known as Dun Aengus, is a famous prehistoric hill fort perched on the edge of a cliff on Inis Mór in County Galway, Ireland. Believed to have been built during the Bronze Age and Iron Age, this ancient site features four concentric walls made of dry stone construction. Visitors can explore the reconstructed walls, chambers, and stairs while learning about its history in a small museum nearby. The fort's impressive size and strategic location overlooking the sea make it a must-visit attraction for those interested in Ireland's ancient past.