Near the Porta S. Paolo, between the Aventine and the river, stands the hill called Monte Testaccio from its being composed almost entirely of potsherds mixed with rubbish. The hill is 150 feet high, and one-third of a mile in circumference. Many conjectures have been hazarded about its origin, which still, however, remains a mystery. The hypothesis which has gained most credit rests upon a passage in Tacitus, in which that historian, after giving an account of the Neronian fire, proceeds to say that Nero intended to have the rubbish carried to the Ostian marshes, and, therefore, gave orders that the corn-ships, after discharging their freight at the Emporium, should take a load of rubbish on their return to Ostia. This explanation appears satisfactory until the peculiar composition of the hill is examined. Nearly the whole mass consists of pieces of broken earthenware, and is not such as we should expect the rubbish left after a fire to be. The absence of bricks may perhaps be explained by the supposition that they were saved in order to be used a second time; but the immense quantity of potsherds still remains to be accounted for. Further, it is said that a coin of Gallienus has been found in such a position on the smaller portion of the hill as to leave no doubt that the accumulation of that part could not have been anterior to Gallienus. A medal of Constantine has also been found in the interior of the larger portion. Bunsen’s explanation that the hill is composed of the rubbish cleared away by Honorius when he restored the walls of Aurelian, and other ingenious hypotheses of the same kind, do not sufficiently account for the peculiar composition of the hill.