The Castel Sant’Angelo was an important political landmark in medieval Rome. Whoever controlled it controlled the city. For instance, in the 10th century, the Crescentii used it as a garrison, which allowed them to seize and imprison two Popes-- John X and Benedict VI-- replacing them with men who would act more favorably towards them. Luckily for the Catholic Church, this plan eventually fell apart when the citizenry rose up and cleared out the space, angry about the new pope. In the aftermath, the church learned from its past mistakes and worked to claim the fortress as its own. This strategy was incredibly valuable in that St. Gregory VII was able to take refuge there in 1084 during a siege of Rome by Holy Roman Emperor Henry IV. Gregory VII would not be the only one to use it as such, as the building became an important refuge for Popes, and its later role as a barracks helped defend Rome (and the Vatican) against enemy invaders. That said, the Castel San’Angelo didn’t always have this military importance. It began as Hadrian’s tomb, whose remnants help form the inner tower structure. The bridge over the Tiber, known as the Ponte Sant’Angelo, was also built by Hadrian. Those are some of the only original structures that remain, as the space was transformed into a fortress in the 5th century, so walls and other defensive elements had to be periodically added into the space. Additionally, when examining the Castel today, it’s important to note that many decorations were added during the Renaissance period to reflect Papal dominance, like statues of St. Peter and St. Paul on the Ponte Angelo. Thus, they should be disregarded when considering what the space would have looked like during early papal processions. Finally, the Castel also has an important religious history. During a plague in 590, there is a story that St. Gregory the Great led an emergency procession by the Castel, and upon arriving, witnessed the Archangel Michael appear over the structure, sheathing a sword and announcing the end of the disease. This event helped spur the Castel’s placement within many processions as a place where a miracle occurred. Thus, in summary, the Castel represented an important marker of the papacy’s physical and religious power with its ability to both loom over the city and provide miracles, which is why it played an important role in papal processions.