Rome is the capital city of Italy. It is also the capital of the Lazio region, the centre of the Metropolitan City of Rome Capital, and a special comune (municipality) named Comune di Roma Capitale. With 2,860,009 residents in 496.1 sq mi, Rome is the country's most populated comune and the third most populous city in the European Union by population within city limits. The Metropolitan City of Rome, with a population of 4,355,725 residents, is the most populous metropolitan city in Italy. Vatican City (the smallest country in the world and headquarters of the worldwide Catholic Church under the governance of the Holy See) is an independent country inside the city boundaries of Rome, the only existing example of a country within a city.

Source: Wikipedia