Dun Ailinne outside Kilcullen, Co Kildare in Ireland, is a place where people came together on regular occasions from the Iron Age until around the sixth century AD. First archaeological excavations were carried out by Dr Bernard Wailes from the University of Pennsylvania in the 1960s and 1970s. In recent years, further investigations have been directed by Dr Susan Johnston from the Department of Anthropology at George Washington University. She talks about unlocking the hill's secrets. Produced by Brian Byrne.