A colonnade is a row of columns that support a roof or a series of arches. It is often used in architecture to create a walkway or to enhance the aesthetic appeal of a building. Colonnades can be found in various styles, including Doric, Ionic, and Corinthian, which are terms that refer to different designs of columns from ancient Greek architecture. Colonnades are commonly seen in public spaces, such as temples, palaces, and galleries. They provide shade and shelter while allowing for open-air movement. Famous examples include the St. Peter's Basilica in Vatican City and the Parthenon in Athens.