Pope Leo, in order to counter the…
852 CE
Pope Leo, in order to counter the Saracen menace definitively, has ordered a new line of walls encompassing the suburb on the right bank of the Tiber to be built, including Old St. Peter's Basilica, which has been undefended until this time.
The Leonine Wall, which defines Rome’s Leonine City, has been constructed following the sack of St. Peter's by Saracens in 846.
Built from 848 to 852 as the only extension ever made to the walls of Rome, this three-kilometer wall completely encircles the Vatican Hill for the first time in its history.
An abortive start had been made by Leo III, but disturbances in the city had suspended work, and the Romans had dismantled the sections that had been begun and used them in private constructions.
Pope Leo IV has used his estate workers, inhabitants from the surrounding countryside, Saracens captured after the sea battle of Ostia in 849 and funding from an imperial Frankish donation, to construct the wall, which runs in an enclosing U-shape from the riverbank at Hadrian's Mausoleum, soon to be Christened the Castel Sant'Angelo, up the slopes of the Vatican hill encircling the basilica and descending again to the river.
The walling is constructed of tufa and tiling, forty feet high, with 44 strong towers at bowshot intervals.
The massive round corner tower that still crowns the Vatican hill has its origins in this construction campaign.
Three new gates gave access to the newly enclosed Borgo.
Two are in the stretch of wall that leads back from the Castel Sant'Angelo: a small postern gate behind the fortified Mausoleum, called the Posterula S. Angeli and later, from its proximity to the Castello, the Porta Castelli, and a larger one, the principal gate through which emperors pass, near the church of St. Peregrino, called the Porta Peregrini, later the Porta S. Petri.
A third gate opens the Leonine City to the rione of Trastevere.
In addition, chain towers have been built along the Tiber river to repel Saracen assaults by water.
A festival celebrates the official completion of the walling on June 27, 852.
Leo has also restored and embellished the damaged Basilica di San Paolo fuori le Mura and St. Peter's: the latter's altar again receives its gold covering (after being stolen), which weighs two hundred and six pounds and is studded with precious gems.
Following the restoration of St. Peter's, Leo appeals to the Christian kingdoms to confront the Arab raiders.