A row of Columns. Often used to support a series of lintels or arches (e.g. arcade on a colonnade). A Colonnade, or reference to one, can be seen below the entablature of any classically influenced building.
In classical architecture, a colonnade denotes a long sequence of columns joined by their entablature, often free-standing, as in the famous elliptically curving colonnades that Bernini added to the facade of Saint Peter's Basilica in Rome, which embrace and define the Piazza. Compare the sequence of baluster forms that go to make a balustrade.