This is a very scenic port and a UNESCO world heritage site. It's fun to explore the narrow streets of the old city. We were ambitious and hiked the city walls up to the fortress overlooking Kotor. The views were great and for impressive views, you don't even have to climb to the top.
From the port of Civitavecchia we had already been to Rome, so instead we went to visit the Etruscan necropolis (a UNESCO world heritage site) in Tarquinia. From Civitavecchia, Tarquinia is a 2 Euro per person bus ride that takes about 30 minutes. The bus stops near the museum in Tarquinia. A combination ticket for the museum and the necropolis is 8 Euros (in 2011). A local bus (0.60 Euros per person) runs from the bus station to the main entrance to the Etruscan necropolis. In the necropolis are a large number of Etruscan tombs with paintings on the walls and ceiling. We walked from the necropolis back to the museum through Tarquinia, which is a picturesque town with a city wall, old churches, and nice views of the countryside. The museum had a very good display of Etruscan artifacts.
Villefranche is a scenic waterfront town with easy access to either Nice or Monaco. We took the train to Monaco (3.70 Euros per person round trip), which took about 15 minutes. The train station in Monaco is high above the waterfront so you can either walk down or use the elevators and tunnel systems that are available from the train station. The waterfront is impressive with lots of yachts in the harbor and great views of the mountains above Monaco. However, if you want to see the palace and the oceanographic museum, you need to head back up the hill using the well landscaped walkways. The trains between Villefranche and Monaco run frequently (about every 30 minutes).