Built starting in the middle of the thirteenth century, with its monumental forms the church of Sant’Agostino is a typical example of mendicant architecture. The brick exterior is very plain, with no decorations. The only element of distinction is the entrance portico built in the nineteenth century by the Sienese architect Agostino Fantastici in conjunction with the remodeling of the Augustinian convent. It has a three-part structure, with a large arch in the center and the lateral architraves supported by two columns topped by open lunettes. Under the portico, which has smooth walls and a vaulted ceiling, is the entrance to the church proper. The wooden door to the church is surrounded by a sixteenth-century marble frame and is set under a classical-style arch. On the façade, at upper right, is a large marble plaque set into the wall, placed there on the occasion of the “Exhibition of Early Sienese Art,” held in 1904, in memory of the sculptor Jacopo della Quercia who, according to sources, was buried in a wing of the cloister of the old convent of the Augustinians. The church has a Latin cross ground plan with one large nave, so as to hold the largest possible number of faithful, as was typical of the mendicant orders. On the right side of the church is the entrance to the private chapel of the Piccolomini family. At the far end of the church are the transept, a large . . .