Built by Constantine as a mausoleum for his daughter Costanza, this building was later consecrated as a church in 1256, and is a fine example of early Christian architecture. The building has a circular form in the tradition of Roman mausoleums. A vestibule porch leads into a circular barrel-vaulted ambulatory which surrounds a central domed space. The ambulatory ceiling vault is decorated with mosaics of geometric motifs and intertwined vines on a white background, late imperial motifs with Christian symbolic significance. The central space is articulated by 12 pairs of coupled Corinthian columns with arches between them, which support the dome lit by 12 clerestory windows.

— JY

Roger H. Clark and Michael Pause. Precedents in Architecture. New York: Van Nostrand Reinhold, 1985. geometry diagram, p183. place-at-center diagram, p198.— Updated edition available at Amazon.com

William L. MacDonald. Early Christian & Byzantine Architecture. New York: George Braziller, 1962. photo of exterior, f15. photo of interior, f16.

Frank Sear. Roman Architecture. London: B.T. Batsford, 1989. ISBN 0-7134-40988. NA310.S44. section drawing, f183, p275. plan drawing, f183, p275.

Russell Sturgis. The Architecture Sourcebook. New York: Van Nostrand Reinhold, 1984. ISBN 0-442-20831-9. LC 84-7275. NA2840.S78. interior perspective drawing, p301.