This tiny, beehive-shaped chapel is one of the best-preserved pieces of early Christian architecture in Ireland. Built sometime between the 7th and 9th centuries A.D., its walls and roof are made entirely of dry stones without mortar—yet the interior stays remarkably dry. (Not quite dry enough, sadly, to avoid damage during the heavy floods that hit Ireland in 2014, though the repairs are seamless.) The small visitor center features displays on the history of the Oratory, plus the obligatory information film. If the visitor center is closed, you can just walk around back and straight up the little path to the next field, where the Oratory is located. (Those with mobility problems should note that you can’t get any closer than this by car, and the uphill walk takes a minute or two from the parking lot.) Nearby is the single surviving tower of 15th-century Gallarus Castle. Tours of the castle can be prebooked at the visitor center—not that there’s much to see inside.