Siena Cathedral, or the Cathedral of Santa Maria Assunta, built in Roman-Gothic Italian style, is one of the most significant churches built in this style in Italy.
The façade, all in white with some red decoration of Siena and serpentine from Prato, is divided into two halves, upper and lower, referring to two distinct phases.
In 1339, it was decided to enlarge the Cathedral.
It only managed to raise the right nave and façade (popularly known as the "Facciatone"). Today the right aisle of five bays, houses the Museo dell'Opera del Duomo. On the left side where you see three arches with large Windows, was built the Royal Palace.
Inside, the nave and chancel are surmounted by a windowsill above a long row of 171 busts of popes, under popes, in the strings, splays are located at regular intervals 36 busts of emperors.
At the beginning of the nave, near the first pair of pillars, you will find two fonts in white Carrara marble, fine work by Antonio Federighi dating from 1458 and 1467.
The pulpit of the Siena Cathedral was designed by Nicola Pisano in a period between 1265 and 1268. It is one of the jewels of the Cathedral, and one of the most important sculptures of the thirteenth century Italian art.
Of considerable importance is the altar built by Piccolomini and the Piccolomini Library .