The history of this church is closely linked to the events of the Castle of Monteriggioni. It was built in 1213, in the year of the foundation of Monteriggioni, and on June 10 1235 when, inside, the delegates from the municipality of Siena and Poggibonsi accepted the conditions of peace with the Florentines. The development of Monteriggiono increased the prestige of the church, so much so that at the end of the 13th century it was promoted to a parish church: the title of Canonica Santae Maire Stemennano was bestowed upon it and the baptismal font was added. Until the beginning of the 14th century it was used for both religious and civilian services. The building consists of a single room with a rectangular end. The façade, which boasts a refined elegance, has a gate with a stone arch surmounted by a circular opening. The inside, renovated in the modern period, has plaster walls and vaulted ceilings. As well as a bell tower from 1299, the church houses a painting from the 17th century of the Madonna of the Rosary, to which a heart-felt local festival is dedicated in October.