historic grotto in the Herrenhäuser Gärten, Hannover Germany.
historic grotto in the Herrenhäuser Gärten, Hannover Germany.

A grotto is an artificial cave which is in general rather small and heavily decorated with rocks, minerals, fossils, sculptures or artworks.

A grotto is a natural or artificial cave used by humans in both modern times and antiquity, and historically or prehistorically. Naturally occurring grottoes are often small caves near water that are usually flooded or liable to flood at high tide. Sometimes, artificial grottoes are used as garden features. The Grotta Azzurra at Capri and the grotto at the Tiberius' Villa Jovis in the Bay of Naples are examples of popular natural seashore grottoes.

This is actually an example that Wikipedia is not always right. We are using the speleological definition, while Wikipedia defines the laymans term, and actually its definition is wrong. First, grotto has nothing to do with water, the fact that Blue Grottoes are at the sea is a coincidence, caves are called grotta in Italian because grotta is the Italian translation of cave. In Italian caverna is used for artificial caverns. In other words the grotto in sea caves is a proper noun from a foreign language.

In Englisch there are two terms for underground structures, cave and grotto. For a long time they were used as synonyms, the word grotto was used for all kinds of caverns. Today the term cave means a natural cavern, while a grotto is an artificial cavern with decorations. However, there are old names and old literature which do not use the term in this strict manner. A common use of the term was to describe a rather small cavern with abundant ornamentation, both natural or artificial. Sometimes it means a single chamber in a cave, or even a well decorated niche in a chamber. But actually, each author used it the way he liked, so you should be quite careful with names and old texts.

The term grottoes on is defined as a small artificial cavern with heavy decorations. They were typically built during the 18th and 19th century, are part of garden and parks architecture. Quite common are buildings which resemble ruined castles, which generate an underground atmosphere inside, are decorated with shells, rocks, and minerals. There are even grottoes with fountains inside. The British term shell house is a synonym.

Another special form of grottoes is the Lourdes grotto. The original Lourdes grotto is a small natural cave with a spring in the village Lourdes, where a young woman had visions of the Virgin Mary. It is a catholic pilgrimage site and decorated like a church. Lourdes Grottoes are more or less replicas of the original grotto, in general completely artificial, most of those grottoes are similar to altars or shrines. They are generally not listed on this website, except if they are actually underground or of great importance.

There is another usage of the term in American English, caving clubs are called grottos in the U.S.A. For obvious reasons we use the term Grotto in the names of the caving clubs, but use caving club instead of grotto throughout the website.