Siena Cathedral. Siena Cathedral is a medieval church in Siena, Italy, dedicated from its earliest days as a Roman Catholic Marian church, and now dedicated to the Assumption of Mary.
It was the episcopal seat of the Diocese of Siena, and from the 15th century that of the Archdiocese of Siena. It is now the seat of the Archdiocese of Siena-Colle di Val d'Elsa-Montalcino.
The cathedral was designed and completed between 1215 and 1263 on the site of an earlier structure. It has the form of a Latin cross with a slightly projecting transept, a dome and a bell tower.
The dome rises from a hexagonal base with supporting columns. The lantern atop the dome was added by Gian Lorenzo Bernini.
The nave is separated from the two aisles by semicircular arches. The exterior and interior are constructed of white and greenish-black marble in alternating stripes, with addition of red marble on the façade. Black and white are the symbolic colors of Siena, etiologically linked to black and white horses of the legendary city's founders, Senius and Aschius. The origins of the first structure are obscure and shrouded in legend. There was a 9th-century church with bishop's palace at the present location. In December 1058 a synod was held in this church resulting in the election of pope Nicholas II and the deposition of the antipope Benedict X. In 1196, the cathedral masons' guild, the Opera di Santa Maria, was put in