CAVAEDIUM, in architecture, a synonym for atrium the central hall or court of a Roman house. Vitruvius lists five types: I. The Tuscanicum. This, the most common type, was without columns, the hole in the roof being supported by the framing of the roof timbers. 2. The Tetrastylon, in which four columns supported the roof at the corners of its opening. 3. The Corinthian, in which more than four columns are employed, so that the cavaedium becomes, in essence, a peristyle (q.v.)• 4. The Displuviatum, where the roof sloped down, away from the opening, instead of towards it. 5. The Testudinatum, in which the entire area was covered by a continuous roof.