You could get a bus or taxi into Marseille town from the port terminal if you did not want to take a tour. Harbour was pretty but lots of roadworks going on there when we visited.
The port is near the town center so you can walk from the ship along the front there is a small road train that you can take for a tour around the city this stops just by the wooden replica Galleon along the front.
The port is Civitavecchia - very pretty beach you can walk to the station about 15 minutes walk along the front here you can get a train into Rome (Roma) for €12 which includes the metro and buses. The journey takes about 1.5 hours and it is easy to get to places of interest by walking or using the hop on hop off buses.
The train goes around Rome and the last stop is a terminus so you cannot go any further this is near the Trevi fountain and also the place you can pick up the tourist buses.
The port was quite nice had a selection of shops and cafes - we did not go outside the port area. Inside you could get a taxi for €40 for 4 people to take you to Carthage which is a suburb of Tunis
Before arriving here we spend an afternoon and evening in Ibiza which was a pretty town with a nice sea front and harbour.
Palma you could walk to the shopping centre or if you felt energetic you could walk to the Cathedral which you can see from the port. Or take a tourist bus outside the port to see the sights.
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