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.
Antonio Barberini
Prior to his election, Pope Urban VIII had been a member of the Sacred Congregation for the Propagation of the Faith. Antonio Barberini was appointed prefect of the Congregation and set about commissioning a new palace, the Palazzo del Propaganda Fide. The construction was started by close Barberini family friend Gianlorenzo Bernini. In 1644, when Antonio was exiled, Bernini was replaced by Borromini who demolished Bernini's chapel and built his own design; the chapel is considered one of Borromini's masterpieces.