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.
Apostolic Palace
Upon returning to Rome in 1377 after the interlude of the Avignon Papacy, which saw Rome subject to civil unrest and the abandonment of several Christian monuments, the popes chose to reside first at Basilica di Santa Maria in Trastevere and then at Basilica di Santa Maria Maggiore. The Vatican Palace had fallen into disrepair from lack of upkeep and the Lateran Palace underwent two destructive fires, in 1307 and 1361, which did irreparable harm. In 1447, Pope Nicholas V razed the ancient fortified palace of Eugene III to erect a new building, the current Apostolic Palace.