A clew to the answer is given on page 87 of my "Ancient Rome," where, in describing the construction of Trajan's forum, and the column which stands in the middle of it, "to show to posterity how high rose the mountain levelled by the emperor" (_ad declarandum quantæ altitudinis mons et locus sit egestus_), I stated that I had been able to estimate the amount of earth and rock removed to make room for the forum at 24,000,000 cubic feet, and concluded, "I have made investigations over the Campagna to discover the place where the twenty-four million cubic feet were carted and dumped, but my efforts have not, as yet, been crowned with success." The place is now discovered. None but an emperor would have dared to bury a cemetery so important as that which I am now describing; and if we remember that it was the open space which was nearest of all to Trajan's excavations, easy of access, that the burying of a cemetery for a necessity of state could be justified by the proceedings of Mæcenas and Augustus, described on page 67 of the same book, and that the change must have taken place at the beginning of the second century, as proved by the dates, and by the construction and type of tombs belonging respectively to the lower and upper strata, I think that my surmise may be accepted as an established fact. Thus vanished the mausoleum of the Lucilii from the eyes and from the memory of the Romans of the second century. Towards the end of the fourth century the Christians, while tunnelling the ground near it, for one of their smaller catacombs, discovered the crypt by accident, and occupied it. The shape of this crypt may be compared to that of Hadrian's mausoleum; that is, it was a hall in the form of a Greek cross, in the centre of the circular structure, and was reached by means of a corridor. The Christians scattered the relics of the first occupants, knocked down their busts, built arcosolia in the three recesses of the Greek cross, and honeycombed with loculi the side walls of the corridor. The transformation was so complete that, when we first entered the corridor, in July, 1886, we thought we had found a wing of the catacombs of S. Saturninus. Some of the loculi were closed with tiles, others with pagan inscriptions which the _fossores_ had found by chance in tunnelling their way into the crypt. Two loculi, excavated near the entrance outside the corridor, contained bodies of infants with magic circlets around their necks. They are most extraordinary objects in both material and variety of shape. The pendants are cut in bone, ivory, rock crystal, onyx, jasper, amethyst, amber, touch-stone, metal, glass, and enamel; and they represent elephants, bells, doves, pastoral flutes, hares, knives, rabbits, poniards, rats, Fortuna, jelly-fish, human arms, hammers, symbols of fecundity, helms, marbles, boar's tusks, loaves of bread, and so on.