My favorite after St Peter Basilica. It is contracted completely of black and white marble, the floors are tiled with biblical narrative, though parts are covered for protection, there are areas where they can viewed. I spent a good part of the day just visiting all areas of the cathedral and at the end had art overload. It was heavy going. I was in Siena some 20 years ago but this time I came specifically to see Siena Cathedral. Siena is an easy one and half hours by bus away from Florence. Its not as busy as Florence and I prefer it to Florence. Florence is one crazy city.