English: Vessagiri Forest Monastery, Anuradhapura, Sri Lanka
These rock shelters were donated to Buddhist monks to use as dwellings, starting in the reign of King Devanampiya Tissa (mid-3d century BC). The site was expanded much later, during the reign of King Kasyapa (473 - 491 AD), at which time it became home to about five hundred monks.
Today's visitor sees only the bare stones - and not all of those, since much of the rock was later carted away and reused elsewhere. But when occupied, the dwellings were finished using wood and other perishable materials.