The Duomo is one of the most important and spectacular buildings in the history of Western architecture. It was begun in 1296 by Arnolfo di Cambio and took more than 200 years to finish. The original design for the building was never finished, as the architect died while working on it. Instead, his sons continued the work, adding the bell tower and the baptistry. The cathedral is built in the form of a Greek cross with four equal arms and is the largest cathedral built in the Gothic style. Its exterior is covered with green and white marble, and its interior is covered with colorful marble and travertine. The ceiling of the nave is made of golden-hued oak and the roof is covered with copper.
The exterior of the cathedral is divided into three sections: the front (or facciata), which is the main entrance; the sides (or laterazze); and the back (or posteriore). The facade was designed by Giotto di Charlesone and is an outstanding example of the use of simple geometrical forms and regularity. The facciata has three levels: the ground floor, which is taken up by the large windows and the two narrow doorways; the first floor, with five large round-headed windows; and the second floor, with three narrow oculus windows and a row of statues representing the virtues. The three stories are articulated by bands of slightly curved brickwork that divide the spaces into bays. Above the bands are geometric patterns of alternating small circular and square openings. The main sculptures on the facade were completed by the Florentine sculptor Nicola Pisano and his workshop. They include the two sets of doors (the lower pair designed by Arnolfo di Cambio, and the upper pair designed by his sons), the large rose window above the main entrance, the three large statues at the corners, and the reliefs over the doorways.
The Duomo is a large building, but it is built in a way as to make it seem much smaller. This is because of the regularity of the exterior and the use of white marble and travertine for the facades and other parts of the structure. The effect is one of simple strength and dignity.
The cathedral has an enormous interior. It has a nave that is almost equal in size to the entire exterior of the building. The nave has a ceiling made of golden-hued oak that is 85 feet high and has a diameter of 92 feet. The entire interior is covered with blue-green and white marble veneers and travertine. There are three levels of arches supporting the ceiling. At the top is the main dome that is covered with a copper-colored ceramic material called “paint” and which has a diameter of 105 feet. The nave is flanked by two aisles, each having two aisles of its own. These aisles have rows of slender columns that support the arches that separate them from the nave. The arches alternate between pointed and round-headed, and they rise to a height of 72 feet.
The interior of the cathedral is vast and majestic. It is illuminated by a rose window that is almost 100 feet in diameter. It has a wooden structure covered with lead-based paint. It is set into a concrete and brick framework that is 24 feet high. The rose window has six lights and it is surrounded by an oculus above the main entrance and another oculus at the apex of each bay. The windows are covered with colored glass that has been arranged in geometric patterns. The effect is one of great splendor.
The entire interior of the cathedral is covered with paintings, frescoes and sculptures. The most famous are the series of 13 chapels that make up the Duomo’s interior. The first chapel on the right as you face the main entrance has a Last Supper painting by Masaccio. The second chapel has a series of frescoes by Masaccio and Filippino Lippi that tell the story of St. Stephen. The third chapel has a fresco by Masaccio depicting the Expulsion of Adam and Eve from the Garden of Eden. The fourth chapel has a fresco by Masaccio that shows the Tribute Money. The fifth chapel has a fresco by Masaccio that illustrates the Wedding at Cana. The sixth chapel has a series of frescoes by Masaccio and Filippino Lippi.