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
The legend was recounted by an Augustinian friar, Giacomo Alberici in his treatise about the Church of Santa Maria del Popolo which was published in Rome in 1599 and translated into Italian the next year. Another Augustinian, Ambrogio Landucci rehashed the same story in his book about the origins of the basilica in 1646. The legend has been retold several times ever since with slight changes in collections of Roman curiosities, scientific literature and guidebooks. An example of the variations could be found in Ottavio Panciroli's book which claimed that the demons inhabiting the tree took the form of black crows. It is not known how far the tradition goes back but in 1726 in the archive of Santa Maria del Popolo there was a catalogue of the holy relics of the church written in 1426 which contained a (lost) version of the ″miracle of the walnut tree″. This was allegedly copied from an even more ancient "tabella" at the main altar. In the 15th century the story was already popular enough to be recounted by various German sources like Nikolaus Muffel's "Description of Rome" (1452) or "The Pilgrimage of Arnold Von Harff" (1497).