Rome's port is Ostia, which is a five-letter word. Ostia was the ancient port of Rome, located at the mouth of the Tiber River. It was founded in the 4th century BC and was the main port of Rome until the 19th century. Ostia was an important commercial center for the Roman Empire, and it was also a major military base. Today, Ostia is a popular tourist destination, with many archaeological sites to explore.