The construction work of this church was started on the second half of the XIII century and was completed towards the end of the XIV century; on the contrary, the bell-tower was an addition of the XVI century. During the XV-XVI centuries tabernacles, chapels were built inside the church and frescoes too adorned its walls. In the following centuries the church got damaged more than once, so it had to go through much restoration work. On the second half of the XIX century many frescoes were recovered: they had been whitewashed after a fire in the XVI century. During the first years of the XX century the church was completely restored. Only the facade is unfinished: according to the original project it was to be covered with carved stones, now present only on the basement floor. In the interior one single nave in Gothic-Franciscan style. On the inner side of the facade: above the side door there is a painting depicting the Miracle of the Donkey; above the main door a fresco portraying the Mystic Wedding of S. Catherina by unknown of the end of the XV century, to the right of the main door a S. Sebastian by unknown of the XIV century. and a Madonna with Child attributed to Domenico Pecori (XVI century); to the left of the main door there are the Redeemer, a Saint, and Emmaus’s Supper, all of which were ascribed by some to Giovanni D’Agnolo di Balduccio, and by others to Parri di Spinello; looking a little bit higher we can sec the wonderful vetrata dell’occhio, a glass window by Marcillat (1524). Along the right wall of the church we can see the Carbonati Chapel with a fresco showing the Madonna of Mercy by Lorentino d’Andrea (1463); in the following chapel a fresco by N. Soggi depicts the Madonna with Child and Saints; and the next chapel was restored in XV century. If we keep on walking we can see the Sinigardi Chapel (1400): a piece of an Assumption, by Giovanni da Ponte (half of the XV century); a chapel preserving a very damaged fresco by Parri Spinello, (Madonna with child and Saints); S. Donnino and S. Niccolò by unknown from Arezzo of the XV century. Moreover we can admire the Gozzari Chapel with a crucifix of the XVII century, and a fresco of  S. Francesco while he gets the stigmata, and higher up frescoes by Spinello, depicting S.Caterina‘s Wedding and the Baptism of Jesus; S.Michael Arcangel (maybe by Parri di Spinello) and an Annunciation by Spinello. The chapel to the right of the sanctuary was entirely frescoed by Spinello Aretino with S .Michael’s Deeds and the Legend of S. Giles; on the altar there is a Triptych (Madonna of the Belt) of the XV century. The most important work in the church and one of the masterpieces of the Renaissance is the Cycle of the True Cross, a cycle of frescoes painted by Piero della Francesca between 1452 and 1464, and situated in the main chapel. The altar of the left chapel preserves the Annunciation and the Saints Girolamo and Francesco by Neri di Bicci (about 1419-91), an Annunciation by unknown, and a Crucifixion by Spinello. On the high altar there is the great crucifix showing S. Francesco kissing Christ’s Feet (by unknown, also called Maestro di S. Francesco). The left wall is filled with a row of chapels: the first one is the Roselli Chapel preserving the Cenotaph dedicated to Jureconsu1t Antonio Roselli from Arezzo. In the next Chapel there is an altar of the XVII century and a painting by Bernardino Santi (XVII century): on the right wall of the third chapel there are a sma11 sanctuary with a crucifix. S. Michael Archangel and S. Caterina from Siena by unknown from Arezzo of the XV century; in the pilaster of the chapel nearby there is a piece of a fresco of the XV century depicting S. Paul: then a chapel entirely dedicated to S. Anton from Padua, with a fresco by Lorenzo d’Andrea (1480). The other chapel is dedicated to the people who died during the First World War and contains a stone altar, few fragments of S. Francesco’s Life by S. Bernardino da Siena. On the pilasters of the chapels there are frescoes dating back to the XIV-XV centuries. On the underground there was another church (3 naves with octagonal pilasters), which today is used as an exhibition-hall.