On the south, S. Mark's joins the Doge's Palace by means of the Porta della Carta. At the base of a column which stands in an angle of the wall are four porphyry figures of knights in chain mail with arms round one another's necks. This group is supposed to have come from Acre. Detached from the main building, and not far from its south-west corner, are two short rectangular columns with Greek inscriptions. They were brought from the church of S. Saba at Ptolemais in 1256. Amongst other interesting spoils there is a slab let into the north wall on which Ceres, holding a torch in each hand, appears drawn in a chariot by two dragons. It seems to be a very early Persian work. But the best known, and certainly the finest gift the exterior of the building can boast, is that of the four bronze horses which stand over the principal entrance. Sent from Constantinople in 1204 by order of the Doge Dandolo as part of the spoils of victory when that city fell to the arms of the Venetians in the fourth Crusade, these horses at one time adorned the triumphal arch of Nero in Rome. Both Domitian and Trajan transferred them in turn to arches of their own; and Constantine conveyed them across the seas to his new capital in the East, where he also put them up over an arch. In 1797, when the Republic of Venice was no more, Napoleon took these already much-travelled horses from S. Mark's façade to Paris and placed them on the top of the Arc du Carrousel. After the peace in 1815 the Austrian Emperor, Francis I. caused them to be returned to their former position, and there they remain to-day.
Three doors open into the cathedral from the vestibule, and two on the north side. The interior strikes one at first as being very dark; but when the eye becomes accustomed to the half-light and is familiar with everything within, this wears off, and the senses are rather soothed than otherwise by the mystic gloom. Indeed, it is a great relief to find oneself inside out of the glare of the Piazza, and, seated in a corner perhaps, quietly contemplating the grand mosaics which cover the vaulting from end to end. It is quite impossible to describe these adequately in a short chapter which deals with other things as well, but noting them in guide-book fashion one observes that those in the aisles on either side of the main entrance depict the Acts and Miracles of the Apostles. On the vaulting of the dome which forms, so to speak, the foot of the Greek cross, is the Descent of the Holy Ghost. The great central dome is covered by twelfth-century mosaics of the Ascension, and the vault between this and the first dome with Christ's Passion and Resurrection. The vaulting of the two domes which compose the arms of the cross is decorated by work of later date; that on the north with the history of S. John, and that on the south with the saints. The chapel of S. John which is in the north transept was converted in the seventeenth century into one dedicated to the Miraculous Virgin of Constantinople. In the south transept also a rededication has taken place; the chapel of S. Leonard being turned into that of the Holy Sacrament.