The heart of the Piazza del Duomo is the Duomo, the medieval cathedral of the Archdiocese of Pisa, entitled to Santa Maria Assunta (St. Mary of the Assumption). This is a five-naved cathedral with a three-naved transept. The church is known also as the Primatial, the archbishop of Pisa being a Primate since 1092.
Its construction began in 1064 by the architect Busketo, and set the model for the distinctive Pisan Romanesque style of architecture. The mosaics of the interior, as well as the pointed arches, show a strong Byzantine influence.