Circus, a Roman racecourse.
Cloaca, a sewer or drain.
Columbarium, literally a pigeon-house—a Roman sepulchre built in many compartments.
Columnar, made with columns.
Compluvium, the open space or the middle of the roof of a Roman atrium.
Corona, in the cornices of Greek and Roman architecture, the plain unmoulded feature which is supported by the lower part of the cornice, and on which the crowning mouldings rest.
Cornice, the horizontal series of mouldings crowning the top of a building or the walls of a room.
Cuneiform, of letters in Assyrian inscriptions, wedge-shaped.
Cyclopean, applied to masonry constructed of vast stones, usually not hewn or squared.
Cyma (recta, or reversa), a moulding, in Classic architecture, of an outline partly convex and partly concave.