Siena’s cathedral is one of Italy’s greatest Gothic churches. Begun in 1196, it was completed by 1215, although work continued on features such as the apse and dome well into the 13th century. The magnificent facade of white, green and red polychrome marble was begun by Giovanni Pisano – who completed only the lower section before his death – and finished towards the end of the 14th century. The mosaics in the gables are 19th-century additions. The statues of philosophers and prophets by Pisano above the lower section are copies; the originals are in the adjacent Museo dell’Opera Metropolitana. In 1339 the city’s leaders planned to enlarge the cathedral and create one of Italy’s biggest churches. Known as the Nuovo Duomo. the remains of this project are on Piazza Jacopo della Quercia, on the eastern side of the cathedral. The daring plan, to build an immense new nave with the present church becoming the transept, was scotched by the plague of 1348. The most precious feature of the cathedral’s interior is the inlaid marble floor, decorated with 56 panels depicting historical and biblical subjects. The earliest ones are graffiti designs in simple black-and-white marble, dating from the mid-14th century. The latest, panels in coloured marble, were created in the 16th century. The most valuable are kept covered and are revealed only from 21 August through 27 October each year. Other drawcards include the exquisitely crafted marble and porphyry pulpit by Nicola Pisano, aided by his equally talented son, Giovanni. Through a door from the north aisle is another of the cathedral’s jewels, the Libreria Piccolomini, built to house the books of Enea Silvio Piccolomini, better known as Pius II. The walls of the small hall have vividly coloured narrative frescoes by Bernardino Pinturicchio, depicting events in the life of Piccolomini.