This is Gallarus Oratory, an incredible example of an early monastic Christian Church which dates from 800 AD. It was built without mortar using "corbel" vaulting which means that it was built with the stones being laid at a slight angle, lower on the outside than on the inside, allowing rainwater to run off. Shaped like an upturned boat, it overlooks the harbour at Smerwick on the Dingle Peninsula.