The location of such a building is however unknown: possible sites are those of the current cathedral, of the Pieve di Sant'Andrea or of San Pier Maggiore.

In 998 a diploma of Emperor Otto III refers to a Palaeo-Christian building located between the "cathedral square" (Piazza del Duomo) and the city's watch tower.

In 1504 Andrea della Robbia was commissioned to undertake the decoration of the archivolt (for which he created a festoon with plant themes and, in the middle, the crest of the Opera di San Jacopo), of the portico as well as of the lunette with bas-reliefs over the central portal, depicting the "Madonna with Child and Angels".

In 1598–1614 the medieval choir was demolished, the side chapels were modified and the original apse was replaced by a Baroque tribune surmounted by a dome designed by Jacopo Lafri, while the main aisle was covered by new cross vaults.

The presbytery pavement is raised, housing the crypt underneath, while the nave and the aisles, separated by columns, have vaults and wooden truss covers respectively.

Next to the chapel's entrance is the tomb of Donato de' Medici (1475), Bishop of Pistoia,[5] attributed to Antonio Rossellino.

In addition, Pace di Valentino, a Sienese goldsmith, created some of the figures surrounding St.

[6] Giglio Pisano executed the large silver statue depicting St. James Enthroned (1349-1353), commissioned as thanksgiving after the end of the Black Death in 1348.

Other works include the Apostles, St. Eulalia, Bishop Atto, St. John the Baptist and Salome by Piero d'Arrigo Tedesco (1380–1390), another Christ in Majesty with St. Anthony Abbot, St. Stephen and the cusp by Nofri di Buto and Atto di Piero Braccini (1394–1398).

[7] The crypt is that of the Romanesque building, and was originally divided into a central and side spaces by columns, and had three apses.