Ostia was an important port city for ancient Rome. Situated 24 km southeast of the capital, between the Tiber River and the Tyrrhenian Sea, its usage and population grew until the river changed course, whereupon the city was abandoned. Today the ruins of Ostia lie 5 km
from the sea.
Founded in 338 BC as a military colony to guard against enemies from the sea, Ostia grew to prominence in the era of the emperors. In 42 AD Claudius started building a harbour which was later opened by Nero. Trajan built another harbour further upstream, and
finally Hadrian restructured the whole layout of the city.
By the second century Ostia was an important commercial centre with upwards of 100 000 inhabitants. Many of their buildings are still intact, much to the joy of archeologists, since storage houses (horreae) and apartment buildings (insulae) have mostly disappeared from other Roman cities. Shops, taverns and laundries also remain, as well as temples and an amphitheatre.
A new town called Ostia di Lido has grown up close to the old Ostia and is much favoured by tourists pining for the seaside.