A grotto is a small cave, either natural or human-made, often near water. Natural grottoes form when waves, streams, or underground rivers carve hollows into rock over thousands of years. These hidden chambers fascinated ancient peoples, who sometimes used them as shrines or sacred spaces. The ancient Greeks believed nymphs lived in grottoes near springs and streams.

During the Renaissance, wealthy Europeans began building artificial grottoes in their gardens: decorative, cave-like rooms with rocky walls, shells, and fountains. These became popular places to escape summer heat or to display art. Some grottoes featured elaborate waterworks with dripping walls and pools, creating cool, mysterious spaces.

Today you might find a grotto at a botanical garden, a zoo, or even at a fancy resort, where a swimming pool might have a cave-like area to swim through. The Blue Grotto in Italy is a famous sea cave where sunlight filters through underwater openings, making the water glow an incredible electric blue.

People sometimes use grotto loosely to mean any small, cozy, cave-like space, even indoors.