Of the two Constantinian basilicas in Rome, the one dedicated to +St. Peter+ was demolished in the fifteenth century; that of +St. John Lateran+ has been so disfigured by modern alterations as to be unrecognizable. The former of the two adjoined the site of the martyrdom of St. Peter in the circus of Caligula and Nero; it was five-aisled, 380 feet in length by 212 feet in width. The nave was 80 feet wide and 100 feet high, and the disproportionately high clearstory wall rested on horizontal architraves carried by columns. The impressive dimensions and simple plan of this structure gave it a majesty worthy of its rank as the first church of Christendom. +St. Paul beyond the Walls+ (S. Paolo fuori le mura), built in 386 by Theodosius, resembled St. Peter’s closely in plan (Figs. 67, 68). Destroyed by fire in 1821, it has been rebuilt with almost its pristine splendor, and is, next to the modern St. Peter’s and the Pantheon, the most impressive place of worship in Rome. +Santa Maria Maggiore+,[15] though smaller in size, is more interesting because it so largely retains its original aspect, its Renaissance ceiling happily harmonizing with its simple antique lines. Ionic columns support architraves to carry the clearstory, as in St. Peter’s. In most other examples, St. Paul’s included, arches turned from column to column perform this function. The first known case of such use of classic columns as arch-bearers was in the palace of Diocletian at Spalato; it also appears in Syrian buildings of the third and fourth centuries A.D. [Footnote 15: Hereafter the abbreviation S. M. will be generally used instead of the name Santa Maria.] [Illustration: FIG. 68.--ST. PAUL BEYOND THE WALLS. INTERIOR.] The basilica remained the model for ecclesiastical architecture in Rome, without noticeable change either of plan or detail, until the time of the Renaissance. All the earlier examples employed columns and capitals taken from ancient ruins, often incongruous and ill-matched in size and order. +San Clemente+ (1084) has retained almost intact its early aspect, its choir-enclosure, baldaquin, and ambones having been well preserved or carefully restored. Other important basilicas are mentioned in the list of monuments on pages 118, 119.