Pope John VIII (872-882) undertook the construction of a fortified wall surrounding the Basilica and its Abbey in order to protect it from invasions. This defensive wall was known as “Joannispolis” or “City of John”.

Pope Gregory VII (1073-1085), abbot of the monastery before being elected Pope, raised the pave of the transept connecting it with the central nave, constructed the bell tower (destroyed in the 19th century) and placed at the main entrance a magnificent Byzantine door [1] adorned by fifty-four panels wrought in damascene silver.

1) In 1070 the Byzantine door was commissioned by Pantaleone, Consul of Amalfi in Constantinople (it was his gift for being redeemed from his sins; as a noble merchant he became wealthy from Muslim and Christian slave trafficking, a trade which was forbidden by the Church). Theodore, an artist of that time, depicted a Christological cycle, an Apostolic cycle (the martyrdom of the Apostles) and a Prophetic cycle. In our time, the door has been restored and transferred to serve as the counter façade of the Holy Door.