Gallarus Oratory, Dingle, County Kerry
The most complete example of early Christian architecture to be found anywhere in Ireland is Gallarus Oratory, on a signposted site a mile inland from Smerwick Harbour. It has been dated to between 800 and 1200 and is a remarkable stone structure, shaped like an upturned boat and measuring 10ft by 15ft inside. It has a small window in the East wall and a narrow 5ft 6in high door in the West side. Although it was built of unmortared stone, it is still waterproof after many centuries of existence. Such oratories were common on monastic sites, but in most cases the roofs have fallen in.
Gallarus Oratory is a must see on your tours of Ireland.