Construction The empress Maria died before 408, but the building may not have been complete at that time; it may have been begun any time between around 400 and 415. even though she was repudiated by Honorius not long after they wed, Thermantia remained an imperial family member by marriage and by birth, and according to
Zosimus she lived in Rome after her divorce from the emperor. Her son
Valentinian III, from her second marriage to
Constantius III, was probably buried in the same mausoleum, but this information is not recorded explicitly. Honorius's sister, Galla Placidia, her husband the
augustus Constantius III, and her sons Theodosius and
Valentinian III were probably buried there. The sarcophagi were buried beneath the floor of the mausoleum, beneath the niches in the walls. Like the
Mausoleum of Constantine connected with the
Church of the Holy Apostles in
Constantinople, the Mausoleum of Honorius was a "symbol of the elevated status of the emperors", since the imperial mausolea of the emperors were symbolic of the
deification of Roman emperors, the . Imperial mausolea during late antiquity were probably used in the manner of a
heroön, for commemorative meals in honour of the deceased, as the centre of a family cult including sacrifices to the dead, and during
Parentalia, the
Roman festival of the dead in February. It appears no such plan was ever contemplated for the remains of Honorius.
Chapel The building was remembered as a mausoleum in the 8th century. The structure is twice referred to as such in the
Liber Pontificalis, in the biographies first of
Pope Stephen II () and then his successor
Pope Paul I (). Knowledge of its identity as a site of imperial burials is not definitively attested and it appears the identity of its occupants had been forgotten and the burials concealed. In 757, Paul I ordered the translation of the relics of St Petronilla to the mausoleum of Honorius. His predecessor Stephen II had already, according to the
Liber, converted the structure adjacent to the chapel of St Andrew into a chapel dedicated to St Petronilla and had made an undertaking to the king of
Francia,
Pepin the Short, that he would translate her relics to the building.. The Mausoleum of Honorius is the domed structure at the extreme top left, behind the rotunda Sant'Andrea and the
Vatican obelisk.
Demolition For the construction of the 16th-century
St Peter's Basilica, the 4th-century Constantinian building was gradually demolished, together with all its chapels, by order of
Pope Julius II. The Mausoleum of Honorius (
S. Petronilla) and the
Vatican Rotunda were demolished to make way for the far larger ground-plan of the Renaissance basilica. The Mausoleum of Honorius itself was destroyed in late November 1519, in the reign of
Pope Leo X. The building has never been the subject of
archaeological excavation, though surviving parts of it may remain beneath the south transept of St Peter's Basilica. == Architecture ==