Built probably in the sixth or seventh century, it was Arnolfo di Cambio who covered it with marble in 1288, building also three new doorways where before there had been but one, that on the west side, which was then closed.  The mere form, those octagonal walls which, so it is said, the Lombards brought into Italy, go to show that the church was used as a Baptistery from the first, though Villani speaks of it as the Duomo; and indeed till 1550 it had the aspect of such a church as the Pantheon in Rome, in that it was open to the sky, so that the rain and the sunlight have fallen on the very floor trodden by so many generations.  Humble and simple enough as we see it to-day before the gay splendour of the new facade of the Duomo, it has yet those great treasures which the Duomo cannot boast, the bronze doors of Andrea Pisano and of Ghiberti.

[Illustration:  PIAZZA DEL DUOMO]

Over the south doorway there was placed in the end of the sixteenth century a group by Vincenzo Danti, said to be his best work, the Beheading of St. John Baptist; and under are the gates of Andrea Pisano carved in twenty bronze panels with the story of St. John and certain virtues:  and around the gate Ghiberti has twined an exquisite pattern of leaves and fruits and birds, it is strange to find Ghiberti’s work thus completing that of Andrea Pisano, who, as it is said, had Giotto to help him, till we understand that originally these southern gates stood where now are the “Gates of Paradise” before the Duomo.  Standing there as they used to do before Ghiberti moved them, they won for Andrea not only the admiration of the people, but the freedom of the city.  To-day we come to them with the praise of Ghiberti ringing in our ears, so that in our hurry to see everything we almost pass them by; but in their simpler, and, as some may think, more sincere way, they are as lovely as anything Ghiberti ever did, and in comparing them with the great gates that supplanted them, it may be well to remind ourselves that each has its merit in its own fashion.  If the doors of Andrea won the praise of the whole city, it was with an ever-growing excitement that Florence proclaimed a public competition, open to all the sculptors of Italy, for the work that remained, those two doors on the north and east.  Ghiberti, at that time in Rimini at the court of Carlo Malatesta, at the entreaty of his father returned to Florence, and was one of the two artists out of the thirty-four who competed, to be chosen for the task:  the other was Filippo Brunellesco.  You may see the two panels they made in the Bargello side by side on the wall.  The subject is the Sacrifice of Isaac, and Ghiberti, with the real instinct of the sculptor, has altogether outstripped Brunellesco, not only in the harmony of his composition, but in the simplicity of his intention.  Brunellesco seems to have understood this, and, perhaps liking the lad who was but twenty-two years old, withdrew from the contest.  However this may be, Ghiberti