Pope Nicholas’s first concern is practical: the reinforcement of the city's fortifications, the cleaning and even paving of some main streets and restoring the water supply.

Ancient Rome’s magnificent array of aqueducts having been destroyed by the hands of sixth-century invaders, Romans have depended on wells and cisterns for their water, and the poor dip their water from the Tiber.

The Aqua Virgo aqueduct, originally constructed by Agrippa, is restored by Nicholas to empty into the predecessor of the Trevi Fountain, a simple basin designed by Leon Battista Alberti.

Nicholas, his heart set on the rebuilding the Vatican, the Borgo district, and St. Peter's Basilica, which is to be the focus of the reborn glories of the papacy, manages to pull down part of the ancient basilica, make some alterations to the Lateran Palace (of which some frescoes by Fra Angelico bear witness), and lay up two thousand five hundred and twenty-two cartloads of marble from the dilapidated Colosseum for use in the later constructions.

In undertaking these works Nicholas is moved "to strengthen the weak faith of the populace by the greatness of that which it sees."

The Roman populace, however, appreciates neither his motives nor their results: a formidable conspiracy for the overthrow of the papal government under the leadership of Stefano Porcaro had been discovered and crushed in 1452.