They are early medieval stone towers of a type found mainly in Ireland, with two in Scotland and one on the Isle of Man.
In Irish, the towers are known as Cloigtheach which mean bell towers, though they may have been used for more purposes.
Generally found near a church or monastery, the door of the tower faces the west doorway of the church.
In this way, it has been possible to determine without excavation the approximate site of lost churches, where the tower still exists.
This proximity to places of worship suggest that the towers were used by Ireland’s early Christian monks in some way.
Surviving towers range in height from 18 metres (60 ft) to 40 metres (130 ft), and 12 metres (40 ft) to 18 metres (60 ft) in circumference; that at Kilmacduagh being the highest surviving in Ireland.