Saint Kieran's Chapel.
Kieran (pronounced KEER-un) was the founder of the city of Clonmacnoise at the intersection of the River Shannon's north-south thoroughfare and a glacial esker's east-west natural roadway across the island.  This, reputedly, is the remains of his hut, or chapel.  The floor's flagstones are recent; farmers had dug so many hands full of dirt from within the walls to spread on their fields for blessing that the walls themselves were in danger of collapse.