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.
Today, artificial grottoes are purchased and built for ornamental and devotional purposes. They are often used as shrines in which to place statues of saints, particularly the Virgin Mary, in outdoor gardens.
Many Roman Catholics visit a grotto where Bernadette Soubirous saw apparitions of Our Lady of Lourdes. Numerous garden shrines are modelled after these apparitions. They can commonly be found displayed in gardens and churches, among other places (see Lourdes grotto).
The largest grotto is believed to be the Grotto of the Redemption in West Bend, Iowa.