Today's Rome reflects the stratification of the epochs of its long history, but it also is a huge contemporary metropolis. Its vast historical centre contains many areas from Ancient Rome, areas from medieval times, many palaces and artistic treasures from the Renaissance era, many fountains, churches and palaces from baroque times, as well as many examples of the Art Nouveau, Neoclassic, Modernism, Rationalism and any other artistic styles of the XIX and XX centuries (the city is in fact considered a living encyclopedia and museum of the last 3000 years of western art). The historical centre is identified as within the limits of the ancient imperial walls. Some central areas were reorganised after the unification (1880–1910 - Roma Umbertina), and some important additions and adaptations made during the Fascist period, with the discussed creation of the Via dei Fori Imperiali, of theVia della Conciliazione in front of the Vatican (for the construction of which a large part of the old Borgo neighbourhood was destroyed) and the founding of new quartieri (among which EUR, San Basilio, Garbatella, Cinecitt?, Trullo, Quarticciolo and, on the coast, the restructuring of Ostia) and the inclusion of bordering villages (Labaro, Osteria del Curato, Quarto Miglio, Capannelle, Pisana, Torrevecchia, Ottavia, Casalotti). These expansions were needed to house the huge increase of population caused by the centralisation of the Italian state.

During the Second World War Rome suffered few bombings (notably at San Lorenzo), and was declared an "open town" (film by Roberto Rossellini). Rome fell to the Allies on June 4, 1944. It was the first capital of an Axis nation to fall.

After the war, Rome continued to expand due to Italy's growing state administration and industry, with the creation of new quartieri and suburbs. The current official population stands at 2.5 million; during the business day workers increase this figure to over 3.5 million. This is a dramatic increase from previous figures, which were 138,000 in 1825, 244,000 in 1871, 692,000 in 1921, 1,600,000 in 1931.

Rome hosted the 1960 Summer Olympics, using many ancient sites such as the Villa Borghese and the Thermae of Caracalla as venues. For the Olympic Games many new structures where created, notably the new large Olympic Stadium (which was also enlarged and renewed to host qualification and the final match of the 1990 FIFA football World Cup), the Villaggio Olimpico (Olympic Village, created to host the athletes and redeveloped after the games as a residential district), etc.

Many of the monuments of Rome were restored by the Italian state and by the Vatican for the 2000 Jubilee.

Being the capital city of Italy, Rome hosts all the principal institutions of the nation, like the Presidency of the Republic, the government (and its single Ministeri), the Parliament, the main judicial Courts, and the diplomatic representatives of all the countries for the states of Italy and the Vatican City (curiously, Rome also hosts, in the Italian part of its territory, the Embassy of Italy for the Vatican City, a unique case of an Embassy within the boundaries of its own country). Many international institutions are located in Rome, notably cultural and scientific ones - such as the American Institute, the British School, the French Academy, the Scandinavian Institutes, the German Archaeological Institute - for the honour of scholarship in the Eternal City, and humanitarian ones, such as the FAO.

Rome today is one of the most important tourist destinations of the world, due to the incalculable immensity of its archaeological and artistic treasures, as well as for the charm of its unique traditions, the beauty of its panoramic views, and the majesty of its magnificent "villas" (parks). Among the most significant resources: plenty of museums - (Musei Capitolini, the Vatican Museums, Galleria Borghese, and a great many others) — aqueducts, fountains, churches, palaces, historical buildings, the monuments and ruins of the Roman Forum, and the Catacombs.

Among its hundreds of churches, Rome contains the five Major Basilicas of the Catholic church: Basilica di San Giovanni in Laterano (St. John Lateran, Rome's cathedral), Basilica di San Pietro in Vaticano (St. Peter's Basilica), Basilica di San Paolo fuori le Mura (St. Paul Outside the Walls), Basilica di Santa Maria Maggiore (St. Mary Major), and Basilica di San Lorenzo fuori le Mura (St. Lawrence Outside the Walls). The Bishop of Rome is the Pope; in his pastoral activity strictly applicable to the city, he is assisted by a vicar (usually a cardinal).