grotto

luola A small cave.
An artificial cavern-like retreat.
A Marian shrine, usually built in a cavern-like structure.
A local organization of cavers that typically organizes trips to caves and provides information and training for caving; a caving club.
1987, National Speleological Society, NSS News, vol. 45-46, p.331:

An earlier attempt to organize a grotto in the Indiana, PA, area in the mid-1970s failed to succeed, but from it developed the informal Chestnut Ridge Explorers Association.

By the mid-1940s members of local grottos (regional clubs of cavers within the National Speleological Society) were exploring Porcupine Cave (Bloch, 1946).

The answer to the question, “Are there any caves in Arizona?” was always the laconic “None to speak of,” with emphasis on the “to speak of.” This secrecy dovetailed with the cave conservation ethic promoted by the local caving grotto.