The Collegiata is the oldest and most important building in San Quirico d'Orcia, a Romanesque collegiate church built in stages between the 11th and 13th centuries. Its three ornate portals are the finest examples of Romanesque decorative carving in the Val d'Orcia — each one different in style and age, reflecting the different craftsmen who worked on the building across more than a hundred years.
The main facade portal features carved columns that rest on crouching lions and interlaced animals. The south portal, on Via Dante, is the most elaborate: two columns supported by telamons (carved figures crouching under the weight) flank an arch covered in intricate knotwork and plant motifs. Inside, the single nave is sober and cool, with a polyptych altarpiece by Sano di Pietro, one of the leading Sienese painters of the 15th century.