the rione of Trastevere. A festival celebrated the official completion of the walling, 27 June 852. In addition, chain towers were built along the Tiber river to repel Saracen assaults by water. In 1083, after refusing to crown Henry IV as the next Holy Roman Emperor, Pope Gregory VII found himself under siege within the Leonine City. After Henry took the city, Gregory fled to Castel Sant'Angelo. Gregory attributed the loss of the Leonine City to famine and negligence and not so much to "the courage of Henry's men". Later, more extensive circumvallation was effected under Pope Pius IV (reigned 1559–1565), when Leo's walling was broken in places. Three further gates had been opened in the walls. In 1870, when the military forces of the Kingdom of Italy captured Rome, overthrowing what was left of the Papal States, the Italian government intended to allow the Pope to keep the Leonine City as a small remnant Papal State. However, Pope Pius IX would not agree to that arrangement, and thus there was a 59-year standoff, when the Popes were a "prisoner in the Vatican", settled in 1929 by the Lateran Treaty, which recognized the sovereignty and independence of Vatican City. See also Borgo Trastevere Index of Vatican City-related articles References Bibliography Gibson, Sheila and Bryan Ward-Perkins. "The Surviving Remains of the Leonine Wall". Papers of the British School at Rome, 47 (1979): 30–57. Hodges, Richard. Mohammed, Charlemagne & the Origins of Europe. Cornell University Press, 1983. Wards-Perkins, Bryan. From Classical Antiquity to the Middle Ages. Oxford University Press, 1984. Subdivisions of Rome Government of Vatican City Rome R. XIV Borgo