The mausoleum of Lucilia Polla and her brother Lucilius Pætus was discovered in May, 1885, in the Villa Bertone, opposite the Villa Albani, at a distance of seven hundred metres from the gate. It is the largest sepulchral structure discovered in my time, and worthy of being compared in size to the mausoleum of Metella on the Appian Way, and the so-called Torrione on the Labicana. It was originally composed of two parts: a basement, one hundred and ten feet in diameter, built of travertine and marble, which is the only part that remains; and a cone of earth fifty-two feet high, covered with trees, in imitation of the Mausoleum of Augustus, with which it was contemporary. The cone has disappeared. The inscription, sixteen feet long, is engraved on the side facing the Via Salaria, in letters of the most exquisite form to be found in Rome. It states that Marcus Lucilius Pætus, an officer who had the command of the cavalry and the military engineers in one or more campaigns, in the time of Augustus, had built the tomb for his sister Lucilia Polla, already deceased, and for himself. The fate of the monument has been truly remarkable. I believe there is no other in the necropolis of the Via Salaria which has undergone so many changes in the course of centuries. The first took place in the reign of Trajan, when the monument was buried under a prodigious mass of earth, together with a large section of an adjoining cemetery. In fact, columbaria dating from the time of Hadrian have been found built against the beautiful inscription of Lucilia Polla; and the inscription itself was disfigured by a coating of red paint, to make it harmonize with the color of the three other walls of the crypt. The whole tract between the Salaria and the Pinciana was raised in the same manner twenty-five feet; and contains, therefore, two layers of tombs,--the lower belonging to the republican or early imperial epoch, the upper to the time of Hadrian and later. Where did this enormous mass of earth come from?