Though much altered through the centuries, the Baptistry of San Giovanni is the forerunner of all such buildings where baptisms take place, a ritual of key importance in the Christian faith. It was built by Constantine in the 4th century and enlarged by Pope Sixtus III about 100 years later. It stands on the site of the baths attached to the home of Constantine's second wife, Fausta, who, emperor's wife or not, was suffocated in the hot room of the baths after having falsely accused Constantine's son by his first wife of having tried to rape her. This exceedingly unpleasant death is an example of one of the accepted Roman methods of dealing with members of the ruling classes who were implicated in scandals of this type. Of the four chapels arranged around the walls of the baptistry, the most interesting is the first on the right as you enter. It has a set of ancient bronze doors whose hinges send out a musical sound when the doors are opened and closed. They probably came from the Terme di Caracalla. Notice also the splendid porphyry columns that support the entire structure, typical of the Romans' love of luxurious and exotic materials.