According to legend, blood flowed from a statue of the Virgin above the altar here after someone threw a pebble at it. This legend motivated Pope Sixtus to rebuild the church in the 1500s on the foundations of an even older sanctuary. For generations after that, its curved porticos, cupola atop an octagonal base, cloisters by Bramante, and frescoes by Raphael helped make it one of the most fashionable churches for aristocrats residing in the surrounding palazzos.