Halfway down the coastal highway to Rome is Civitavecchia. You might dismiss it as a big modern port, but don’t – the old town center and the beach esplanade are lovely, and there are many excellent bars, restaurants (especially for seafood), and shops in the area.
The modern city was built on an ancient Etruscan settlement, and the port harbour was constructed by the Romans in the 2nd Century. In the early middle ages it was a Byzantine stronghold, and was raided numerous times by the Saracens once rule had passed to the Papal States in 728, who eventually built the massive Michelangelo fortress and arsenal which still stand today to protect the town and the nearby port of Rome. Well worth the visit, and the nearby Ficoncella baths north of the city, which are still popular today!