A Grotto is a small cave, usually near water and often flooded or liable to flood at high tide. Associated with spirits, mermaids, pirates, smugglers, treasure.

The word comes from Italian grotta, Vulgar Latin grupta, Latin crypta, (a crypt). It is related to the word grotesque: in the 15th century, Italians unearthed ancient Roman houses decorated in strange arabesques of garlands and animals. Because of the caves in which they were discovered, this form of decoration was given the name grotesque.

The creation of artificial grottoes was a huge architectural fashion in the Renaissance in both Italy and France from the 15th to the 17th century. The outside of these was usually designed like an enormous rock or a rustic porch or rocky overhang; inside one found a temple or fountains. The inside was often decorated in stalactites and shells (sometimes made in ceramic), herms and mermaids, mytholgical subjects (sleeping gods or the rivers). They were cool places to retreat, but they could also serve as baths, chapels or simply as bizarre and mysterious spots with often highly symbolic decorations. They would eventually give rise as well to cascading fountains in Renaissance gardens.

The Grotto of the Redemption is the largest grotto in the world, and is located in West Bend, Iowa.

The grotto of Catherine de Medici's château in Paris, the Tuileries, was renowned. It was designed by Bernard Palissy. One also finds grottos in the gardens designed by André Le Nôtre for the Palace of Versailles.

Santa's Grotto is usually an area set up in a department store at Christmas for an actor dressed as Santa Claus to distribute gifts to children.