The new Rome, the 'Third Rome', underwent many changes. First, a massive expansion of the city started. The size of the town had been much the same since medieval times, and the papal town lived comfortably with the Aurelian Walls with room to spare. Within a few decades the city had spread also outside the ancient walls, and entirely new areas were developed. Second, the town centre suffered many changes too. A renaissance quarter constructed on top of the ancient Imperial Fora was completely demolished to create space for the new Piazza Venezia and the massive Vittoriano monument, and an entire wing of the Palazzo Venezia had to be moved to a nearby location. The space in front of Campidoglio and the Piazza Bocca della Verità were overrun by traffic as the Via Teatro Marcello was opened. Similar urban interventions were made to create the Corso Vittorio Emanuele connecting Piazza Venezia and the Vatican.

Of new constructions in this period the Palazzo di Giustizia comes to mind, besides the Vittoriano. The enclosure of the Tiber River is also from this period.