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.
Pope Paschal I
Paschal rebuilt three basilicas of Rome: Santa Prassede, Santa Maria in Domnica, and Santa Cecilia in Trastevere. Paschal is credited with finding the body of Saint Cecilia in the Catacomb of Callixtus and translating it to the rebuild the basilica of Santa Cecilia in Trastevere. Paschal also undertook significant renovations on Basilica di Santa Maria Maggiore. In addition, Paschal added two oratories to Old St. Peter's Basilica, SS. Processus et Martinianus and SS. Xistus et Fabianus, which did not survive the 16th century renovation of St. Peter's.