The Palazzo Vescovile (Bishop's Palace) is located on the left side of the square that Enea Piccolomini decided to build in order to give his birthplace, Corsignano, the structure of a city of humanism, an ideal city for people. The Palace's architecture was Gothic and it was donated by Enea to his closest collaborator, the Vice Chancellor of the Holy See Rodrigo Borgia, who later became Pope Alexander VI. The facade is very simple, with a portal and two rows of Guelph cross windows. The coat of arms of the Borgia family, who made it their residence, stands out on the corner. There is no certainty about how long Borgia resided in Pienza, as he did not willingly leave Rome except with the noblewoman Giulia Farnese, a young girl forced by her family to be the Pope's lover in order to favour the ascent to cardinal of her brother, Alessandro Farnese.
The Bishop's Palace now accommodates the Diocesan Museum of Pienza and consists of eleven rooms in which important pieces that bear witness to the figurative art of great artists of the time are kept. One of these is Pietro Lorenzetti, a master from the Siena school, with his splendid Madonna di Monticchiello, and Luca Signorelli, described by Vasari as an artist with an enigmatic style, capable of celebrating the God Pan and also the Virgin Mary, a humanist painter focused on that eoplatonic culture in which the profane was reinterpreted in the light of Christian values.