The interior was formed by massive concentric walls, the spaces between which were vaulted and divided into cells for the deposit of the urns containing the ashes of the illustrious dead. A great alabaster vase found near the Mausoleum in 1777, and placed in the Vatican Museum, was probably one of these. We know from various passages of Roman authors that the first burial which took place here was that of the young Marcellus, the favourite nephew of Augustus, who died at Baiæ[101] in B.C. 23, and the last, that of the Emperor Nerva in A.D. 98. Trajan was buried under his column. The Mausoleum of Hadrian became the Imperial tomb in A.D. 138.[102] During the 160 years which intervened, the ashes of Agrippa, Octavia, the mother of Marcellus, Drusus, Caius and Lucius, Augustus himself and Livia, Germanicus, Drusus, son of Tiberius, the elder Agrippina, Tiberius, Antonia (wife of L. Domitius), Claudius and Britannicus were deposited here. Besides these there must have been a great number of other friends and relations of the Imperial family buried here. Only one of all the inscriptions recording these burials is now extant. It is engraved on a pedestal, which bore the urn where the ashes of the elder Agrippina, the wife of Germanicus and mother of Caligula, lay. In the inscription on this pedestal Caligula is called Augustus, showing that the burial took place after his accession, in accordance with the account of Agrippina’s banishment by Tiberius. The pedestal was hollowed out and used in the Middle Ages as a measure for corn, and is still inscribed with the words RUGITELLA DI GRANO. It may now be seen in the courtyard of the Conservator’s Palace on the Capitol. At the same time, and at a spot between the Mausoleum and the Corso were found six cippi of travertine, recording the burning of the bodies of four of the children of Germanicus, Tiberius Cæsar, Caius Cæsar, Livilla, and one whose name is erased. The remaining two cippi record the burning of the bodies of a son of Drusus, and of one of the Flavian family. It is evident that these belonged to the Ustrina Cæsarum, a place described by Strabo, as quoted above, where the corpses of the dead were burnt and the formal ceremony of collecting the bones took place. The cippi may still be seen in the Vatican Museum. The Mausoleum remained closed after Nerva’s burial until the capture of Rome by Alaric in A.D. 409, when the Goths broke it open in their search for treasure, and scattered the ashes of the Cæsars to the winds. It was then probably that the alabaster vase mentioned above was removed from the Mausoleum and carried to the Ustrina where it was found.