48年至852年期間修筑,长3公里,首次将梵蒂冈山完全包围起来。。城墙上开了三个城门。852年6月27日,举行了竣工庆祝活动。 FerdinandGregorovius, Annie Hamilton, tr. History of the City of Rome in the Middle Ages
On the Constitution of Papal Conclaves (Edinburgh 1878) 125-129. FerdinandGregorovius, The History of Rome in the Middle Ages (translated from the fourth