We now see distinctly the large corbels[167] all round the building at a certain height, about six feet below the present level of the soil, for carrying the boards of the great floor covered with sand called the arena, upon which the athletes wrestled, the wild beasts were killed, and the persons condemned to death were torn to pieces by wild beasts; so that the martyrdom of the early Christians who were condemned to death in this manner took place on the sand of the _arena_, and not on the soil of the _area_. These corbels, in some instances, at the south end of the building, have the ends of them built into the old tufa wall, which is cut away to receive them. This old wall is not so regular in plan as the great work of the Flavian Emperors, the architect of which probably intended to destroy these old walls ultimately. Dio Cassius (himself a Roman senator) gives a vivid description of scenes which took place in this Amphitheatre[168] in his presence, in the time of Commodus (as has been said), which leaves no doubt about the matter. Similar scenes are described in the time of Nero. The whole of the arena was, in fact, supported in all directions by the walls of the chambers or passages not more than ten feet apart; one object of which, no doubt, was to carry the great boarded floor, that could be removed at pleasure by the order of the emperor, and replaced as readily[169]. The excavations of 1874 and 1875[170] very much astonished the people in Rome, and more especially the English visitors, who had been long accustomed to consider the _area_ and the _arena_ to be the same thing; they were amazed to see the whole of the area undermined with walls[171]. The walls that were first seen are for the most part brick walls of the fifth century, and the inscription[172] found there in 1814 records that they had been repaired by Lampadius, prefect, A.D. 442. This was after they had been much damaged by an earthquake. Another inscription records repairs of the _arena_ and the _podium_ by Basilius, prefect and consul, A.D. 508, after another earthquake. A long subterranean passage[173] at a considerable depth, leads out at the south-east end in the direction of the church of S. Clement; this passage passes under a number of square-topped arches or doorways, and has rather the appearance of having been a state entrance at the time that the level of the street was as low as that passage, that is, before the filling-up of the foss-ways, which began in the second century. On each side of this passage is a long narrow vaulted chamber parallel to it, under the corridor, and in the pavement of each of these chambers is a series of six round holes lined with hard copper or bronze, for a pivot to work in; they are somewhat worn, and in a straight line one behind the other. The most probable use for these was for a windlass or capstan to be worked in each, and by these means to drag along the vessels in the canals before mentioned, as