As the centuries passed Rome was still a constant centre of conflict. Other invaders, both Franks and Vandals, had succeeded to the Goths. The Lombards, in the eighth century, besieged the castle of St. Angelo, but the city was preserved by the defences of Gregory the Great. Next, the Saracens attacked it but recoiled before the fortifications of Pope Leo IV, who created the Leonine city by enclosing the Vatican with a long wall, which began at St. Angelo and ran round St. Peter’s, turned then to the left and completed the circuit by regaining the river below the gate of S. Spirito. The wall was forty feet high and nineteen feet thick, built with forty-one towers. It was pierced by three gates, a small one near St. Angelo, a larger one, the St. Peregrini, afterwards the Porta Vindaria, and a third at S. Spirito. The castle itself was reconstructed and strengthened and became the key to the whole line. It was closed at one end by an iron chain across the Tiber. When finished, the work was solemnly dedicated to heaven and the blessings of all the angels and apostles were invoked upon the new Rome, with a fervent prayer that it might be preserved ever pure and impregnable. This Leonine city was to become the stronghold of the popes, a constant bone of contention, fought for by many masters and passing through many hands. Its history has been stirring and eventful, and it would be interesting, were it possible, to record the many strange vicissitudes through which it passed, and to describe at length the notable persons, famous and infamous, who ruled it from time to time. A very cursory glance will suffice to indicate their leading characteristics, their rare virtues and vices; the good they did, and also the evil; their great ambition for the Church and themselves, which frequently led them to take desperate measures to gain their ends. Factions and dissensions were ever rife; rivals forever struggled for the supreme power,--such as the renegade pope, Stephen VI, who dared to produce the corpse of his deceased predecessor, Formosus, for trial on a trumped-up charge. The body was disinterred eight months after burial, dressed in pontifical robes and publicly arraigned for usurping the See of Rome. As there could be no defence, sentence was passed in default, the corpse was decapitated, the three fingers of the right hand used in consecration were cut off and the remains cast into the Tiber. Stephen himself was soon called to account after a brief reign of three months, was dethroned and cast into prison.