On this day in 1339, the General Council of Siena voted to accept the extraordinarily ambitious “Duomo Nuovo“ project for Siena Cathedral. The Sienese had already decided in 1316 to expand their Duomo with a new choir extending for two bays over a baptistery built into the hillside below as a foundation (see plan, c). Doubts were raised about the project’s feasibility, and a committee of experts (including three Florentines) advised the Cathedral Works to abandon the plan and build a new, larger building. The Sienese solution was to transform the existing structure into a large transept, building a new, enormous nave on the southeast flank (see plan, d). Just over 60% of the council members approved the plan; and the project would ultimately fail. Though partly vaulted by mid-century, the piers and vaults of the new north aisle were demolished after 1357 when they were assessed to be defective. The south aisle and facciatone (enormous facade) are still preserved today, housing the Opera del Duomo museum and standing as a testament to Sienese civic pride, ambition, and hubris.
Siena, plan of the present cathedral, begun after 1215, and the Duomo Nuovo, c. 1339–48: (a) crypt; (b) bell-tower; © choir extension over baptistery; (d) Duomo Nuovo; (e) dome; (f) Piccolomini Library; (g) sacristy
Reference: Enzo Carli and H. B. J. Maginnis. “Siena.” Grove Art Online. Oxford Art Online. Oxford University Press.
Further reading: The Cathedral of Siena and the Cathedral Museum by Enzo Carli (1995).