The Baptistery of San Giovanni Battista, flanked by an imposing stairway leading up to the level of the Piazza del Duomo, was built beneath the Cathedral, perhaps under the supervision of Camaino di Crescentino, capomastro (master builder) starting in 1299. It is decorated with a marble façade, left unfinished, which rises above the viewer, due to the limited space of the square in front of it. . . .