Traditionally, pilgrims in Rome (as well as devout Romans) visit the seven pilgrim churches () in 24 hours. This custom, mandatory for each pilgrim in the Middle Ages, was codified in the 16th century by Saint Philip Neri. The seven churches are the four major basilicas (St Peter in the Vatican, St Paul outside the Walls, St John in Lateran and Santa Maria Maggiore), while the other three are San Lorenzo fuori le mura (an Early Christian basilica), Santa Croce in Gerusalemme (a church founded by Helena, the mother of Constantine, which hosts fragments of wood attributed to the holy cross) and San Sebastiano fuori le mura (which lies on the Appian Way and is built above the Catacombs of San Sebastiano).