Saint Dedication of the basilicas of Saints Peter and Paul, Apostles

Old St. Peter's Basilica consisted of the church buildings that stood, from the 4th to 16th centuries, where St. Peter's Basilica stands today in Vatican City. Construction of the basilica, built over the historical site of the Circus of Nero, began during the reign of Roman Emperor Constantine I. The name "old St. Peter's Basilica" has been used since the construction of the current basilica to distinguish the two buildings. Construction began by orders of the Roman Emperor Constantine I between 318 and 322, after his conversion to Christianity and took about 40 years to complete. Over the next twelve centuries, the church gradually gained importance, eventually becoming a major place of pilgrimage in Rome. Papal coronations were held at the basilica, and in 800, Charlemagne was crowned emperor of the Carolingian Empire there. In 846, Saracens sacked and damaged the basilica. The raiders seem to have known about Rome's extraordinary treasures. Some basilicas, such as St. Peter's Basilica, were outside the Aurelian Walls, and thus easy targets. They were "filled to overflowing with rich liturgical vessels and with jeweled reliquaries housing all of the relics recently amassed". As a result, the raiders destroyed Saint Peter's tomb and pillaged the holy shrine. In response Pope Leo IV built the Leonine wall and rebuilt the parts of St. Peter's that had been damaged. By the 15th century, the church was falling into ruin. Discussions on repairing parts of the structure commenced upon the pope's return from Avignon. Two people involved in this reconstruction were Leon Battista Alberti and Bernardo Rossellino, who improved the apse and partially added a multi-story benediction loggia to the atrium façade, on which construction continued intermittently until the new basilica was begun.