Here the attraction is the Dover Castle. There is a city bus right outside the port that will take you either there or in the little town center where you can catch a train to London or Canterbury. We visited the castle and the guided tour of the war tunnels, very interesting.
Le Havre is not a very nice city but right at the dock you can rent a car, it has to be done before as they do not have many. ( le havre rent-a-car). We drove to Mont St Michel ( 3 hours and very easy) and it was just an amazing place. On the way back we also stopped in Honfleur a nice Normandy seaside artist town.
We took the funicular to the top of the mountain ( 40 minutes walk from the ship), saw the crazy monkeys and the beautiful St Michael's cave, the old castle and war tunnels and walked down the mountain to the ship. The town itself is just stores, stores and stores.
The ship left from Amsterdam and we had time to enjoy the beautiful city but beware of the bikes, they are everywhere !!! We took a bus (Arriva) near the train station to Volendaam, Marken ( ferry) and back to Edam, the countryside was spectacular and we bought many souvenirs far cheaper than the prices in Amsterdam. In Amsterdam you can walk everywhere but you need a week to see everything !!!
Lisbon is a fabulous city but we were there on a Monday and all the museums were closed except for the Sao Jorge castle in town that is worth a visit if only for he spectacular views. We hopped on a bus near the ship (17A) got to Rossio place and took the train to Sintra a beautiful little town on the coast, we visited the Imperial Palace ( very nice) and did a tour of town on a little train. Good buys in the shops. We then came back and walked through Lisbon and finally took a taxi to the ship.