A wall of iron bars confronted her, transforming a natural grotto into a prison cell.

They stood on the threshold of a beautiful natural grotto, which was dimly lit by some source that Flint could not im- mediately identify.

Antoninus retired to Monte Aureo himself and lived in a natural grotto.

They went from the bathing room back through the bedroom; it looked even more like a natural grotto than the bathing room had.

Even the tourists, interested mainly in sight-seeing, confined their attention to the vast grottoes, natural and excavated, of the deep interior.

If not for the perfectly arched walls and roof and the smooth concrete surface, they could have imagined themselves in an immense natural grotto.

Instead, she slid off the bench and walked casually toward a natural grotto whose emptiness reflected her footfalls.

The monk lived and died in a small natural grotto, on top of a cliff above the sea.

These monuments were originally natural grottoes, which tradition assigned as habitations to the local nymphs.

The crypt was dug in a tuff rock and includes some natural grottoes.