Santa Maria del Popolo
Soon after its transfer to the prestigious Lombard Congregation Santa Maria del Popolo was reconstructed between 1472 and 1477 on the orders of Pope Sixtus IV. This was part of the ambitious urban renovation program of the pope who presented himself as "Urbis Restaurator" of Rome. The medieval church was entirely demolished and a new three-aisled, Latin cross shaped basilica was built with four identical chapels on both sides, an octagonal dome above the crossing and a tall Lombard style bell-tower at the end of the right transept. The result of this reconstruction was an early and excellent example of Italian Renaissance architecture in Rome. In spite of the many later changes the basilica essentially kept its Sistine form until today.
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).