Trequanda is a picturesque medieval village, developed around a 13th century castle of which a cylindrical tower with battlements still remains today.
During the XIII-th century the castle of Trequanda passed to the Scialenga's Counts. They belonged to the political faction of the Ghibellines (Empire's supporters) and used the castle to receive all the ghibellines escaping from Siena, supporting this latter the Guelphs (Papacy's supporters). Due to its role as a shelter place, Trequanda subdued numerous sieges by the army of the Republic of Siena along the century and finally this latter conquered the village. The historic centre is an airy and sunny piazza overlooked by the splendid Romanesque church dedicated to San Pietro and Sant'Andrea. Built in the 13th century, the façade in slabs of white and dark stone achieves a chromatic effect that is fairly rare in this area.
Inside there is a frescoed Ascension by Sodomiaand a triptych by Giovanni di Paolo.