San Giovanni in Oleo

San Giovanni in Oleo is a chapel adjacent to the church of San Giovanni a Porta Latina in Rome. It commemorates the place where, according to legend, in 92 CE, at the hands of the emperor Domitian, the apostle John was immersed in a vat of boiling oil from which he emerged unharmed. Tradition relates that, having failed to execute the apostle, Domitian exiled him to the island of Patmos where John wrote the biblical Book of Revelation. It is supposed that John later died and was buried in Ephesus where a large basilica was built to house his relics. He is held to be the only one of the Twelve Disciples to have been spared from martyrdom.

Although the current building is not ancient, the small centralized form - customarily employed by the Romans for martyria, mausolea and other memorial purposes - may have been inspired by an earlier structure. Documentary sources seem to indicate that San Giovanni a Porta Latina was in existence by the end of the 5th century.