Battistero di San Giovanni
The Battistero di San Giovanni is the often sited as the oldest building in central Florence. The roots of the site go back to Roman times, but the current octagonal Romanesque structure was actually completed around 1059. Why is the Baptistery a separate structure from the cathedral? In earlier times, the heathen hordes could not enter the cathedral until they had been duly baptized into the Church. Hence, it was a separate building.
These are the famed East Doors of the Baptistry, also known as the Gates of Paradise.
Look familiar to those of you in the city by the bay? No coincidence! A replica of these doors are installed at the Grace Cathedral in San Francisco, which we saw two years ago.