One of the most ancient and enduring sites for baptism in Rome is the church of San Giovanni in Fonte. This church is in fact a baptistery, and houses the font for the Lateran Basilica, the cathedral of Rome. The Emperor Constantine sponsored its construction in the year 315, and it is therefore the oldest baptistery in the world. It is the model for nearly all later baptisteries, including perhaps the font in your own parish church.