San Stephano has a double range of interior columns, taken from Roman temples, the one supporting an entablature, and the other a series of arches. The church has been much modified by successive alterations, and the interior is ornamented with curious paintings, representing the sufferings of the martyrs. The baptistery of St. Angeli is smaller, but has preserved its original form in a greater degree. [Illustration: ST. VITALE, OF RAVENNA.] [Illustration: THE TEMPLE OF MINERVA MEDICA.] St. Vitale is a type of structure much copied in subsequent buildings. It is itself modelled on the so-called temple of Minerva Medica, differing only in having an octagon instead of a decagon plan. Of this Fergusson gives the following account: “It certainly belongs to the best days of the Roman empire, if, indeed, it be not a Christian building, which I am very much inclined to believe it is, for on comparing it with the baptistery of Constantine and the tomb of St. Contanza, it shows a considerable advance in construction on both of these buildings, and a greater similarity to San Vitale, at Ravenna, and other buildings of that time, than to anything else now found in Rome. It has a dome eighty feet in diameter, resting on a decagon of singularly light and elegant construction. Nine of the compartments contain niches, which give great room on the floor, as well as variety and lightness to the general design. Above this is a clerestory of ten well-proportioned windows, which give light to the building; perhaps not in so effective a manner as the one eye of the Pantheon, though by a far more convenient arrangement, to protect from the elements a people who did not possess glass. “So far as I know, all domed buildings erected by the Romans up to the time of Constantine, and, indeed, long afterward, were circular in the interior, though they were sometimes octagonal externally. This, however, is a polygon both internally and on the outside, and the mode in which the dome is placed on the polygon shows the first rudiments of the pendentive system, which was afterward carried to such perfection by the Byzantine architects, but is nowhere else to be found in Rome. It probably was for the purpose of somewhat diminishing the difficulties of this construction that the architect adopted a figure with ten instead of eight sides.” The plans of the temple of Vesta and of the baptistery of Constantine have been placed here next to one another in order to show the transposition of the columns from the exterior to the interior, which is the chief distinction between the Roman circular buildings and Christian baptisteries. [Illustration: THE TEMPLE OF VESTA, SOMETIMES CALLED THE TEMPLE OF HERCULES.] [Illustration: THE BAPTISTERY OF CONSTANTINE.] VII. THE BYZANTINE STYLE.