Worth a visit
The Museo Delle Sinopie is located in the Piazza del Duomo across from the Tower of Pisa. I bought the special ticket that gives access to all the square's museums and monuments, except the tower, so I don't know how much the individual entry costs. At the museum, you can see original sketches of the works that adorn the Cathedral, the Baptistery, and others. There's also an exhibition of old costumes. Not a must-see, but worth a visit and small enough to see quickly.