According to Wikipedia, Civitavecchia is "a city and comune of the Metropolitan City of Rome ... a sea port on the Tyrrhenian Sea ... 60 kilometres (37 miles) west–north–west of Rome." It's in the far north–western corner of Lazio, the region of which Rome is the capital.
Ostia is (quoting Wikipedia again), "a large neighbourhood in the X Municipio of the comune of Rome ... near the ancient port of Rome, which is now a major archaeological site known as Ostia Antica."
© Haydn Thompson 2022