The Gates.
There were naturally four gates to this enormous structure, one at each end, and one in the middle of each side; and the same arrangement was followed in all the other amphitheatres. By what names these gates were called, and whether these names were special for each particular building, or general for all, is a question still undecided, and also which was the state entrance. It is commonly said that in the Colosseum the state entrance was on the northern side, next the Esquiline Hill, because there is no number over that arch as there is over the other arches, but this was probably the case with all the four entrances; the other three gates are destroyed. The excavations in 1875 have been supposed to shew that the passage on the southern side towards the Cœlian did not lead direct to the palace of Commodus, but was carried round the outer line of the building to the south-east end, near S. Clemente; the natural entrance from the palace of Nero would be from the gate at the east end, and not on the north side. The names of the gates are not easily fixed; one was called Porta Libitinensis, and from this door the bodies of those who were killed were carried out, as we learn from Lampridius in the life of Commodus[224]. They were carried out of this gate on a special bier provided for the purpose, called sandapila, as is mentioned by Juvenal[225], and explained by the old Scoliast. This name is sometimes written sanavivaria, as in the Acta Martyrum Felicita et Perpetua[226]. The word libitina signifies death, or a funeral, or a bier; it is used also by Horace in his Odes[227], and explained by the Scoliast in the same manner, and by Martial in his Epigrams[228]. It appears that the name of sandapilaria and libitinensis were synonymous. Another gate was called Porta Prætoria, probably that at the south-east end, opening from the road to the Vivarium at the Prætorian Camp. Another, Porta Sacra, probably that at the north-west end, opening to the Via Sacra. The Meta Sudans was close to this gate, and was supplied with water by tubes, as Seneca mentions in his Epistles[229]. His fifty-seventh letter is full of lamentation for the fate of the athletes.
The name of cochlea is given to one of the doors of the amphitheatre, which led from the cavea to the arena. This name is used by Varro[230], and has puzzled all the commentators; it need hardly be said that cochlea is literally “a snail,” and the name has been supposed to apply to some narrow doorway; but the name is well known in mediæval Latin as applied to a winding or newel staircase, popularly called a corkscrew-staircase, and there are two such staircases leading from the substructures or cavea to the level of the arena, one on either side, at the south-east end of the great central passage in the Flavian amphitheatre, to which there can be no doubt that this name was applied. Trajan’s column is frequently called columna cochlea, because there is such a staircase inside of it.