Santa Maria del Popolo
The architect or architects of this innovative project remain unknown due to a lack of contemporary sources. Giorgio Vasari in his "Lives" attributed all the important papal projects in Rome during Sixtus IV to a Florentine, Baccio Pontelli including the basilica and monastery of Santa Maria del Popolo. Modern researchers deemed this claim highly dubious and proposed other names among them Andrea Bregno, a Lombard sculptor and architect whose workshop certainly received important commissions in the basilica. The fundamental differences between the façade and the interior suggest that maybe more than one architect was working on the building.
Santa Maria del Popolo
After the Della Rovere era, the basilica lost its prominent role as a papal church but it remained one of the most important pilgrimage churches in the city. This was shown on 23 November 1561 when Pope Pius IV held a solemn procession from St. Peter's to the Basilica of Santa Maria del Popolo on the occasion of reopening the Council of Trent. Building works went on in the Chigi Chapel in a slow pace until the 1550s. The last important Renaissance addition was the Theodoli Chapel between 1555 and 1575 with rich stucco and fresco decoration by Giulio Mazzoni.