Ages, Rome kept its status as Papal capital and holy city for centuries, even when the Papacy briefly relocated to Avignon (1309–1377). Catholics believe that the Vatican is the last resting place of St. Peter. Pilgrimages to Rome can involve visits to many sites, both within Vatican City and in Italian territory. A popular stopping point is the Pilate's stairs: these are, according to the Christian tradition, the steps that led up to the praetorium of Pontius Pilate in Jerusalem, which Jesus Christ stood on during his Passion on his way to trial. The stairs were, reputedly, brought to Rome by Helena of Constantinople in the fourth century. For centuries, the Scala Santa has attracted Christian pilgrims who wished to honour the Passion of Jesus. Other objects of pilgrimage include several catacombs built in imperial times, in which Christians prayed, buried their dead and performed worship during periods of persecution, and various national churches (among them San Luigi dei francesi and Santa Maria dell'Anima), or churches associated with individual religious orders, such as the Jesuit Churches of Jesus and Sant'Ignazio. 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). Cityscape Architecture Rome's architecture over the centuries has greatly developed, especially from the Classical and Imperial Roman styles to modern fascist architecture. Rome was for a period one of the world's main epicentres of classical architecture, developing new forms such as the arch, the dome and the vault. The Romanesque style in the 11th, 12th, and 13th centuries was also widely used in Roman architecture, and later the city became one of the main centres of Renaissance, Baroque and neoclassical architecture. Ancient Rome One of the symbols of Rome is the Colosseum (70–80 AD), the largest amphitheatre ever