Granite has a typical way of weathering, which forms pits in the rock face called tafoni or taffoni. There are many millions of small ones, but only few which are big enough to form a shelter. They are formed mostly by chemical weathering or corrosion, the parts of the granite which are less resistant against acids in the rain water are removed faster, so minimal differences in the chemistry of the rock result in massive differences in erosion. While the name originates from Corsica, and there are actually tafoni in abundance, they can be found all over world.
Oriu, plural Orii, is the name for such a giant tafoni which was used to build a cave house, by closing it with a wall. They were first built in the 16th and 17th century by shepherds as temporary shelters. They lived in the coastal plain, which is named transhumance, but during summer they went to the mountains with their Corsican Mouflon and needed temporary homes. While most were constructed for habitation, like this one at Canni, others were intended for storage like the one for grain and hay at Chera. Orii are not that well known by present-day Corsicans, since they are often hard to find and hidden by maquis. But there are probably about one hundred of them.
Corsica has no karst caves, so there are only small caves, and not that many, so any cave of a certain size, no matter how it formed, was used as a shelter. So there are actually numerous Oriu which were not built into erosional caves, but into tectonic caves or boulder caves.