Fodor's Expert Review Gallarus Oratory

One of Ireland's most interesting sights is also one of the country's best-preserved early Christian churches. Gallarus Oratory dates from the 7th or 8th century and ingeniously makes use of corbeling—successive levels of stone projecting inward from both side walls until they meet at the top to form an unmortared roof. The structure is still watertight after more than 1,000 years.