By the architect Gherardo Mechini, the Tuscan grand dukes built the basilica following various miraculous events. The most important of these events was when, after a long period of drought, a water source sprang forth in 1602.
A loggia with rounded arches preceded the sanctuary's construction. The latter contains fourteen lunettes by Giovanni da S. Giovanni depicting the miraculous events linked to the sanctuary and to the miraculous image venerated here.
With a single nave and a coffered ceiling, the interior has some very interesting works. These include the organ donated by Grand Duchess Cristina of Lorraine, paintings with St. Francis, St. Jerome, St. Charles Borromeo, and St. Sebastian from the 17th century, and a marble high altar containing the miraculous fresco, the work of the 15th-century Florentine school.