Placed in the spot where the chapel belonging to the shoemakers’ guild once stood, dedicated to the Birth of the Virgin Mary, this grand altar was conceived to hold a small panel of The Virgin of Humility painted by Paolo di Giovanni Fei around the end of the fourteenth century and earlier positioned on an ancient altar in the cathedral. This majestic structure was intended by the Cardinal as a means of glorifying the Virgin Mary, protector of the Sienese and dedicatee of the cathedral, while the same time honoring the memory of his uncle Pius II, remembered in the epigraph that runs above the large central niche. A second inscription along the base of the altar indicates that the monument was destined to be the cardinal’s own tomb, but since he died in Rome after just a short time as pope, he was buried in Saint Peter’s, and from there later moved to the church of Sant’Andrea della Valle, together with his uncle Pius II. The execution of this marble complex was commissioned around 1480 to the Lombard sculptor Andrea Bregno, who worked on it together with some assistants, giving shape to a monumental structure. The front, whose form recalls a triumphal arch, presents a spacious central niche containing the altar proper, topped by a marble altarpiece that now holds a reproduction of The Virgin of Humility by Paolo di Giovanni Fei (the original has been kept since the . . .