Rome is located in the central-western portion of the Italian Peninsula, within the Lazio (Latium) region, along the shores of the Tiber River. The city center is about 24 kilometers inland from the Tyrrhenian Sea, but the city territory extends to the shore, where the southwestern district of Ostia is located. The historic center of Rome was built on seven hills: the Aventine Hill, the Caelian Hill, the Capitoline Hill, the Esquiline Hill, the Palatine Hill, the Quirinal Hill, and the Viminal Hill. Rome is the capital of the Lazio region and the largest and most populous city in Italy.