Siena's Cathedral, or Duomo di Siena, is a medievil church dedicated as a Roman Catholic church to venerate the Blessed Virgin Mary.

It was built between 1215 and 1264 and designed in part by the Gothic master, Nicola Pisano. The lower half of the facade was designed by his son, Giovanni in 1285. The Facade's upper half was added in the 14th century, during Siena's height of wealth and power. In this era of prosperity, there were plans to build the Duomo Nuova, so large that it would dwarf even St Peter's Cathedral in Rome. Unfortunately, the Plague struck in 1348 and the giant cathedral was never completed. In the 19th century the Duomo was extensively restored and it is still functioning as a sacred place today.

The Duomo features black and white stripes of marble as black and white are the symbolic colors linked to the legendary black and white horses of the city's founders,  Senius and Aschius. From the exterior you can see the tall, square belltower, called a campanile. There is the entrance, the Porto del Perdono (the Door of Forgiveness) in the south, portraying a medallion bust of the Virgin and Child by Donatello and on the north side of the Duomo, a stone is set into the wall is inscribed with "Sator Square." The West Facade is the main entrance to the Cathedral and designed by Giovanni.