The Museo dell'Opera Metropolitana is better known as the Museum of the Duomo because it was founded in 1870 to house the collection of art work coming from the Cathedral, Sienna's metropolitan church.

The Museum building forms part of the Duomo Nuovo and the best known work is the great Maestà painted between 1308 and 1311 by Duccio di Boninsegna for the high altar where it was located until 1505.
The Maestà is the first true masterpiece of Sienese painting and has two faces The front side showed the enthroned Madonna surrounded by the angels and saints with the patron saints and protectors of Sienna seen in the lower part. The back shows 26 episodes of Christ's Passion, ranging from His entrance into Jerusalem to the supper in Emmaus.
Also worth noting is the Madonna "with the big eyes", as it is known, a work from the middle of the 13th century. On the eve of the battle of Monteaperti, on September 4th 1260, the people of Sienna solemnly dedicated their city to the Virgin Mary in front of this Madonna.
Then there is the beautiful painting from 1330 by Simone Martini portraying Blessed Agostino Novello and the four miracles obtained through his intercession.In addition there is the Nativity of the Virgin Mary, the principal work of Pietro Lorenzetti's mature period, painted in 1342.
Works of sculpture include the statues of the patriarchs, prophets and sybils, originally sculpted by Giovanni Pisano for the façade of the Duomo, a Madonna with Child by Donatello, and a beautiful relief work by Jacopo della Quercia made between 1410 and 1425 where you can see Cardinal Antonio Casini in adoration before the Madonna and Child with saints, including his patron St Antony Abbot.