Callixtus established the practice of the absolution of all repented sins. Hippolytus was especially upset by the pope's admitting to communion those who had repented for murder, adultery, and fornication.
A spot on which he had built an oratory was claimed by tavern keepers, but the Emperor decided that the worship of any god was better than a tavern. This is said to have been the origin of Santa Maria in Trastevere. In fact the Church of St. Callistus is close by, containing a well into which legend says his body was thrown, and this is probably the church he built, rather than the more famous basilica.
It is possible that Callixtus was martyred around 222, perhaps during a popular uprising, but the legend that he was thrown down a well has no authority. He was buried in the cemetery of Calepodius on the Aurelian Way[?]. His relics were translated in the ninth century to Santa Maria in Trastevere.
He is honored as a martyr in Todi, Italy[?], on August 14. Saint Callixtus is depicted in art wearing a red robe with a tiara (sign of a pope); or being thrown into a well with a millstone around his neck; or with a millstone around his neck. Often there is a fountain near him.