Man-made underground passage in Killacorraun

Killacorraun preserves a man-made underground passage inside its rath, hidden beneath a shallow depression near the north-west scarp. The structure likely served the people who built the rath, giving them a route below the ground when storms raged or danger approached. That much is clear from the remains. What is less certain is whether the passage led to a chamber, a well or another entrance now lost.