Here is the east side of the inner enclosure wall of Dun Aonghasa (Dun Aengus) where it ends at a cliff edge over the Atlantic ocean.
Visible are the last 60 feet or so of the limestone strata supporting the inner ring.
When first constructed, the inner ring was complete, the western side 1,000 feet from the cliff.. Today’s form of a semi-circle was created by nature when the force of Atlantic Ocean waves eroded the cliff, undercutting the strata.
Look close to see a fracture where the next block of limestone will fall into the waves.
Wishing a blessed All Saints Day (November 1st) for all my readers.
Reference: wikipedia Dún Aonghasa, Sea Campion