Siena Cathedral (Il Duomo)
Inside the place is equally impressive with art by Donatello, Bernini and early Michelangelo. Some of the best pieces such as Duccio di Buoninsegni's Maesta have been moved next door to the Museo Dell'Opera. Unlike other cathedrals where you are craning your neck to see magnificent ceilings and frescoes, here you need to look down at the mosaic floor. The whole floor is tiled and is one of the most impressive in Italy. There are 56 panels of biblical and historic scenes, some of which are covered and only revealed for a few months each year (around August to October, extra fee payable).
Not content with having such an impressive Duomo, Siena's ambitious ruling families in the 14th century decided to expand the church into the Nuovo Duomo, doubling the size of the existing structure. The plan was stopped by the plague and the Museo Dell'Opera occupies the new nave that was completed.