“The cause of final ruin to this monument,” is described by Nibby to have been the resentment of the citizens against a French governor who espoused the cause of the anti-pope (Clement VII.) against Urban VI. in 1378. It was then that the marble casings were all torn from the walls and used as street pavements. A drawing of Sangallo of 1465 shows the upper part of the fortress crowned with high square towers and turreted buildings; a cincture of bastions and massive square towers girding the whole; two square-built bulwarks flanking the extremity of the bridge, which was then so connected with these outworks that passengers would have immediately found themselves inside the fortress after crossing the river. Marlianus, 1588, describes its double cincture of fortifications,--“a large round tower at the inner extremity of the bridge; two towers with high pinnacles, and the cross on their summits, the river flowing all around.” The Castle began to assume its present aspect under Boniface IX. in 1395. John XXIII., 1411, commenced the covered way to the Vatican, which was finished by Alexander VI.; and roofed by Urban VIII., in 1630. By the last named pope the great outworks of the fortress were built under Bernini, and furnished with cannon made from the bronze roof of the Pantheon. Under Paul III. the interior was decorated with frescoes, and a colossal marble angel erected on the summit, in place of a chapel (S. Angelo inter Nubes), built by Boniface XIV. for the existing angel of bronze, by a Dutch artist, Verschaffelt. Of the Castle, as we now see it externally, only the quadrangular basement is of the time of Hadrian; the round tower is of that of Urban VIII., its top added by Paul III. The four round towers of the outworks, called after the four Evangelists, are of Nicholas V., 1447.