The Gallarus Oratory  is  an early Christian church located on the Dingle Peninsula, County Kerry, Ireland.   According to local legend, if a person climbs out of the oratory via the window, their soul will be cleansed

 It is built with stones from the Dingle Beds of the Upper Silurian Old Red Sandstone. The stones were laid at a slight angle, lower on the outside than on the inside, thus allowing rainwater to run off. This design has kept the interior relatively dry despite the lack of mortaring, allowing the building to remain in excellent condition.