lla, was destroyed in the sixteenth
century; the other, called the Church of S. Maria della Febbre, met
with the same fate during the pontificate of Pius VI. Their exact
situation in relation to the modern basilica is shown by the
accompanying diagram.

Mention of the structure, with its classical denomination of
"Mausileos," appears in the life of Stephen II. (A. D. 752). To fulfil
a promise which he had made to Pepin, king of France, that the remains
of Petronilla, who was believed to be the daughter of Peter, should
be no longer exposed to barbaric profanations in their original
resting-place on the Via Ardeatina, but put under the shelter of the
Leonine walls near the remains of her supposed father, he selected one
of these two rotundas, which became known as the "chapel of the kings
of France." The early topographers of the Renaissance, ignorant of its
history, gave a wrong name to the building, calling it the Temple of
Apollo. That it was, however, of Christian origin, is proved not only
by the fact that a temple could never have been built across the
_spina_ of the circus, and by the technical details of its
construction, which show it to be a work of the end of the fourth or
the beginning of the fifth century, but also by historical evidence.
In 423 Honorius was buried in the mausoleum close by S. Peter's
(_juxta beati Petri apostoli atrium in mausoleo_). In 451 the remains
of the Emperor Theodosius II. were removed from Constantinople to the
_mausoleum ad apostolum Petrum_. In 483 Basilius, prefect of the
Praetorium, summoned the leaders of the clergy and of the laity to the
mausoleum _quod est apud beatissimum Petrum_. A precious engraving by
Bonanni, No. lxxiv. of his volume on the Vatican, represents the
outside of one of the rotundas, the nearest to the obelisk of the
circus. The architecture of the building, so similar to the tomb of S.
Helena at Torre Pignattara, gives some conception of the enormous
downfall of Roman art and civilization, when we compare it with the
tombs of Augustus and Hadrian.

The discovery of the imperial graves which filled the two rotundas did
not take place at one and the same time. Their profanation and robbery
was accomplished in various stages, by various persons; and so little
has been said or written about them, that only in these last years has
de Rossi been able to reconstruct in its entirety this chapter in the
history of the destruction of Rome.

[Illustration: ROTUN