Rome is the capital of Italy and a special comune (named Comune di Roma Capitale). Rome also serves as the capital of the Lazio region. With 2,877,215 residents in 1285km2, it is also the country's most populated comune. It is the fourth-most populous city in the European Union by population within city limits. It is the center of the Metropolitan City of Rome, which has a population of 4.3 million residents. Rome is located in the central-western portion of the Italian Peninsula, within Lazio (Latium), along the shores of the Tiber. The Vatican City is an independent country inside the city boundaries of Rome, the only existing example of a country within a city: for this reason Rome has been often defined as capital of two states.Rome's history spans more than 2,500 years. While Roman mythology dates the founding of Rome at around 753 BC, the site has been inhabited for much longer, making it one of the oldest continuously occupied sites in Europe. The city's early population originated from a mix of Latins, Etruscans and Sabines. Eventually, the city successively became the capital of the Roman Kingdom, the Roman Republic and the Roman Empire, and is regarded as the birthplace of Western civilisation and by some as the first ever metropolis. It was first called The Eternal City (Urbs Aeterna; La Città Eterna) by the Roman poet Tibullus in the 1st century BC, and the expression was also taken up by Ovid, Virgil, and Livy. Rome is also called the "Caput Mundi" (Capital of the World).