A good example of
corballing (as I would have spelled it) can be found in the
beehive huts on the
Skelligs in
Ireland. These
hemispherical structures were created by laying rings of stone on top of each other, each ring being smaller than the last. The
cusp of the
curve is then capped with a massive
keystone. The weight of this stone is distributed throughout the walls of the structure, allowing the whole thing to stand up for over a thousand years, without the aid of any kind of
mortar.
Ironically, all of the original beehive huts, dating from the ninth century, are still intact on Skellig Michael, while an oratory built in a more familiar rectangular shape, with the use of mortar, lies in ruins, despite being built several hundred years later.