The Collegiata is San Quirico's principal church, a Romanesque building whose facade carries some of the most finely carved stone in the Val d'Orcia. The main portal is an elaborate work of the 12th century, with interlocking arches supported on columns resting on carved lions, the whole densely decorated with plant forms and human figures in a controlled exuberance typical of the best Romanesque work.
The interior is simpler than the exterior promises, but contains a polyptych by Sano di Pietro, the 15th-century Sienese painter, and a triptych by Giovanni di Paolo. The wooden choir stalls are worth looking at: carved in the mid-15th century by Antonio Barili, they are considered among the finest of their period in Tuscany.
The church is free to enter and usually open during daylight hours. The west facade, facing the main street, gives you a good view of all three doorways together.