Vasari says: "He made three sketches, extravagant in style and most beautiful, of which the Pope selected the least costly; this was executed much to his credit, as may now be seen." To what extent he was responsible for the other sixteenth-century gates of Rome, including the Porta del Popolo, which is commonly ascribed to him, cannot be determined; though Vasari asserts that Michelangelo supplied the Pope with "many other models" for the restoration of the gates.

Indeed it may be said of all his later work that we are dealing with uncertain material, the original idea emanating perhaps from Buonarroti's mind, but the execution having devolved upon journeymen.
Pius IV.

charged Michelangelo with another great undertaking, which was the restoration of the Baths of Diocletian in the form of a Christian church.

Criticism is reduced to silence upon his work in this place, because S.Maria degli Angeli underwent a complete remodelling by the architect Vanvitelli in 1749.

This man altered the ground-plan from the Latin to the Greek type, and adopted the decorative style in vogue at the beginning of the eighteenth century.
All that appears certain is that Michelangelo had very considerable remains of the Roman building to make use of.