The site was first used in Neolithic times, dating back to around 2000BC. There are a number of burial mounds within and around the site of a fort. The fort is circular with four embankments and ditches, which was further secured by its location in an area of bog land. The remains of 'Old Croghan Man', a well preserved Iron Age bog body who is believed to have died (possibly as a sacrifice) between 362 and 175 BC, was found in a bog close by. The remains are in the National Museum of Ireland in Dublin.