In Rome, the capital of the Roman Empire, there are many baptisteries from as early as the fourth and fifth centuries AD. They are among the oldest in the world and make clearly visible traces of the Christianization of the capital of the Roman Empire. In the early fourth century, almost all baptisms in Rome were celebrated by the Roman bishop in the Lateran baptistery, probably built by the Emperor Constantine who gave a legal status to the Christian religion after the bloodstained persecutions under the Emperor Diocletian. In this building, the new Christians were baptized in a 10 meters broad font while water was poured from seven silver deers, a golden lamb and silver sculptures of Christ and St. John the Baptist.

Towards the end of the fourth century the majority of the population of Rome embraced the new religion. It became necessary to build new baptisteries , for all those who wanted to be baptized during the baptismal liturgies twice a year, one at Easter and one at Pentecost.  

New baptisteries for a new, Christian Rome

Several among the 25 "titulus" churches still exist, but only some of their baptisteries have been found, many of them only recently: San Crisogono, San Marcello al Corso, Santa Cecilia in Trastevere, San Clemente, San Marco, San Lorenzo in Lucina (and Santa Croce in Gerusalemme which is not among the 25 titulus churches) . These new discoveries have led to e new interest in this kind of building. The baptisteries played an important historical role, because it was in their basins that most common Romans recieved Christian baptism in the fifth century and their children after them. These buildings thus had a certain importance in the religious changes between Roman Antiquity and the Middle Ages. The interest in the baptisteries has also grown together with the general interest in Late Antiquity, a period of changes in which modern man easily can recognize himself.