If you are wondering what exactly is this Facciatone: on August 23, 1339, it was decided to enlarge Siena Cathedral (the construction work had already begun in February). The project intended to keep the existing church, which was supposed to become the transept of the new cathedral, modifying the dome and creating a fore-structure with two aisles and a nave, six bays and a new apse. After 1348, due to the economic recession caused by the Black Death, which had decimated the population, and problems of statics that had emerged, the construction slowed down and eventually stopped. Following the abandonment of the Duomo Nuovo project, the construction was partially demolished. However, an enormous "trunk" still remained from this impressive building project, consisting of the facciatone, the side walls and the northeast facing nave. If that’s not enough, there is something more, not included in the OPA Pass. For example the Porta del Cielo (Gate of Heaven) is open to the public for some periods of the year with its own ticket.