The vast wealth which the jubilee of 1450 had poured into the Papal coffers[1] he employed in beautifying the city of Rome and in creating a stronghold for the Sovereign Pontiff.

The mausoleum of Hadrian, used long before as a fortress in the Middle Ages, was now strengthened, while the bridge of S.Angelo and the Leonine city were so connected and defended by a system of walls and outworks as to give the key of Rome into the hands of the Pope.

A new Vatican began to rise, and the foundations of a nobler S.Peter's Church were laid within the circuit of the Papal domain.

Nicholas had, in fact, conceived the great idea of restoring the supremacy of Rome, not after the fashion of a Hildebrand, by enforcing the spiritual despotism of the Papacy, but by establishing the Popes as kings, by renewing the architectural magnificence of the Eternal City, and by rendering his court the center of European culture.

In the will which he recited on his death-bed to the princes of the Church, he set forth all that he had done for the secular and ecclesiastical architecture of Rome, explaining his deep sense of the necessity of securing the Popes from internal revolution and external force, together with his desire to exalt the Church by rendering her chief seat splendid in the eyes of Christendom.