At the Ballynastaig stone fort, lies what is known as a Souterrain. A souterrain (from French ‘sous terrain’, meaning “under ground”) is a name given by archaeologists to a type of underground structure associated mainly with the Iron Age.
It is believed that they were used to store food or act as a hiding place during times of strife. At the Ballynastaig fort, there is a narrow alley way that leads to five steps which lead down into the souterrain.
Once in the narrow doorway, the souterrain widens out to about 2.5 metres and stretches back for at least 7 metres. The roof is lintelled with tightly packed stone beams running width-wise. The manner in which the souterrain has stood the test of time, is testament to it’s builders.