At the south-east end, under the old entrance, at the present level of the ground, a long passage has been found, with a series of square-topped arches, at about fifteen feet below that level. This has been traced further to the south, beyond the limits of the building; it must have led from the great foss-way in that direction. There is a large and deep drain extending from the south end of the Colosseum, turning at an angle and passing at the foot of the Claudium to the Meta Sudans, near the arch of Constantine. It was continued under the present Via di S. Gregorio, and the south-east end of the Palatine[161]. In one part, near the south end, on the western side of the central passage at the lowest level, which is twenty-one feet below the present level of the ground and the top of the walls of the substructure, the two ancient tufa walls (before mentioned) remain nearly perfect, with the vertical grooves opposite to each other, evidently for lifts to slip up and down, and in each instance in the wall on one side a hollow is cut, for the counter-weight to work up and down[162]. These lifts are very near together in the outer passage, in front of the _podium_, but far below the bottom of it. Behind each of them is a small square chamber under the passage in front of it, with a narrow entrance to it, and a small stream of water running in front for the use of the animals, as these are plainly the dens for the wild beasts to be placed in temporarily, and there is just space enough for the animal to pass through into the wooden cage (_pegma_[163]), which had two doors, one at the side, the other at the top. When the cage on the lift was pulled up to the level of the floor of the stage or arena, under one of the trap-doors, the upper part was pulled up by a cord from below along with the trap-door, and the animal thus placed at liberty sprang out on to the stage. In the original pavement, which remains round a great part in the passages, behind the place for each of the lifts, is a round hole for the socket of a pivot to work in, evidently for the windlass for winding up the cord[164]. It is calculated that there was one of these lifts in front of each arch, and a den behind each, all round the _enceinte_ of the building, so that all the wild beasts could spring on to the stage at once with tremendous effect. The persons in the lower gallery were protected by strong nets, and by bars that turned round on pivots, so that the claws of wild beasts had no hold upon them.