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.
Gian Lorenzo Bernini
Bernini was also a leading figure in the emergence of Roman Baroque architecture along with his contemporaries, the architect Francesco Borromini and the painter and architect Pietro da Cortona. Early in their careers they had all worked at the same time at the Palazzo Barberini, initially under Carlo Maderno and, following his death, under Bernini. Later on, however, they were in competition for commissions, and fierce rivalries developed, particularly between Bernini and Borromini. Despite the arguably greater architectural inventiveness of Borromini and Cortona, Bernini's artistic pre-eminence, particularly during the reigns of popes Urban VIII (1623–44) and Alexander VII (1655–65), meant he was able to secure the most important commissions in the Rome of his day, the various massive embellishment projects of the newly finished St. Peter's Basilica, completed under Pope Paul V with the addition of Maderno's nave and facade and finally re-consecrated by Pope Urban VIII on 18 November 1626, after 150 years of planning and building. Bernini's design of the Piazza San Pietro in front of the Basilica is one of his most innovative and successful architectural designs. Within the basilica he is also responsible for the Baldacchino, the decoration of the four piers under the cupola, the Cathedra Petri or Chair of St. Peter in the apse, the chapel of the Blessed Sacrament in the right nave, and the decoration (floor, walls and arches) of the new nave.