This is located on Piazza del Duomo at number 9, and it contains artworks from both the Cathedral and the Baptistery.

The building was originally the headquarters of the public body known as the Opera, established to oversee the construction and maintenance of the sacred buildings. The building itself was originally a 16th century residence and is distinguished by the marble bust of the Grand Duke Cosimo I above the doorway. Descriptions of the most important works follow.