Its plan, however, seems to have remained unchanged, and shows a further progress towards what afterwards became the Byzantine style than is to be found either in the Minerva Medica or in San Vitale. It is in fact the earliest attempt to amalgamate the circular church with one of a square shape; and except that the four lateral colonnades are flat segments of circles, and that there is a little clumsiness in the angles, it is one of the most successful designs handed down from that early age.
The dome as it now stands is octagonal, which the first dome certainly could not have been. Its diameter is 70 ft., nearly equal to that of the Minerva Medica, and the whole diameter of the building is internally 142 ft.
In front of the church, in the street is a handsome colonnade of pillars, borrowed from some ancient temple—it is said from one dedicated to Hercules; this leads to a square atrium, now wholly deprived of its lateral arcades; and this again to a façade, which has been strangely altered in modern times. Opposite this, to the eastward of the church, is an octagonal building, apparently intended as a tomb-house; and on the north side a similar one, though smaller. On the south is the baptistery, about 45 ft. in diameter, approached by a vestibule in the same manner as that of Constantine at Rome, and as in the tomb of his daughter Constantia; all these, however, have been so painfully altered, that little remains besides the bare plan of the building; still there is enough to show that this is one of the oldest and most interesting of the Christian churches of Italy.
The building now known as the baptistery at Florence is an octagon, 108 ft. in diameter externally. Like the last-mentioned church, it was originally the cathedral of the city, and was erected to serve as such apparently in the time of Theodelinda, queen of the Lombards. If this was so, it certainly had not originally its present form, and most probably those columns which now stand ranged round the walls, at that time stood in the centre, as in the Roman examples. If the original roof was of wood, it was probably in two stories, like that of the baptistery of Constantine, or it may have been a dome of more solid materials, like that of the Sta. Costanza.
At the same time when the new cathedral was built, the older edifice appears to have been remodelled both internally and externally by Arnolpho da Lapo, and both its form and decoration so completely changed, that it must now be considered rather as a building of the 13th century than of the 6th, in which it seems originally to have been erected.
- In this building they now show a sarcophagus of ancient date, said to be that of Galla Placidia, daughter of Theodosius. She, however, was certainly buried at Ravenna; but it may be of her time, and in these ages it is impossible to distinguish between baptisteries and tombs.