Augustus began the construction of his mausoleum in ca 28 B.C., soon after he defeated Anthony and Cleopatra. It is a circular structure about 300 feet in diameter and about 140 feet high. It was composed of a number of concentric circular walls, the outer of which were filled in to provide support for the structure. Only the lower third of the monument is preserved.
The focus of the mausoleum was a large, hollow, cylindrical column, on top of which a large statue of Caesar Augustus was placed—it is thought that the Prima Porta statue of Augustus is a small marble representation of this original bronze statue. The Prima Porta statue was discovered on the Via Flaminia in the villa of the empress Livia.
This central space of the mausoleum as well as the surrounding circular corridor, are where the marble funerary urns that contained the ashes of the deceased were placed. The urn of Augustus occupied the central, most prominent, space.
Many members of the royal families were buried here. As were the Emperors Tiberius, Claudius, and Nerva (the last emperor to be buried here).
The mausoleum was entered from the south by a long corridor (dromos) that was flanked by two obelisks from Egypt—now erected in the Piazza del Quirinale and Piazza dell'Esquilino.
After the Late Roman Period, building materials of the mausoleum were removed and used in other structures in Rome. Over the years the significant remnants of the structure were used as a fortified castle, a formal garden, an arena for bullfights and firework displays, and finally as a concert hall in the 19th-20th centuries.
The mausoleum was reopened to the public in Mach 2021 after years of restoration.