ostia

Ostia refers to two related places: the ancient port city of Ostia Antica and the modern seaside district Lido di Ostia in the municipality of Rome, Lazio, Italy. Both are located at the mouth of the Tiber River, about 30 kilometers from central Rome.

Ostia Antica was founded in the 4th–3rd century BCE as Rome's harbor and grew into the principal port of the Roman Republic and early Empire. Its ruins include a forum, warehouses, baths, a theater, and residential blocks, together preserving a large portion of the urban plan of a Roman port city.

By late antiquity the harbor silted up and trade declined, contributing to Ostia's abandonment. The area was gradually depopulated and fell into neglect during the Middle Ages, though the landscape later became the focus of archaeological interest and preservation.

The modern Ostia, or Lido di Ostia, developed as a seaside resort in the 20th century. It is connected to Rome by the Rome–Lido railway and today serves as a popular beach destination and residential district, with a waterfront and fishing activity near the harbor area.

Today, Ostia Antica is one of Italy's notable archaeological sites, offering extensive ruins such as the large theatre, the Decumanus and Cardo main streets, baths, and mosaic floors. The site attracts visitors seeking insight into Rome's port economy and daily life.