A pyramid of rough stones, raised for a memorial or mark of some kind, usually over a burial but also as a landmark or monument. A cairn could also indicate where something valuable was stored. In America, a cairn is a structure of rounded stones. The word is often used as a synonym for barrow in areas where burial mounds were normally of stone. In Scotland and Ireland, the custom was for friends to add a stone to the pile when they passed a cairn.