I'm a theme-park junkie, and have been to Europe 26 times, IIRC. I did my mission in France and Belgium.
On this trip, I flew into Brussels did Walibi Belgium, drove up to the Netherlands to go to Efteling park. Took a train from Brussels-Dusseldorf. Then flew to Helsinki. Visited the city and the theme park (Linnanmäki) and took a train up to Tampare for a day trip to Särkänniemi. Then took the overnight cruise from Helsinki to Stockholm, went to Gröna Lund, the Vasa (ship) museum and visited the city. Took a train to Oslo. Went to TusenFryd, saw the Scream painting, Frogner park and a lot of other stuff. Great dinner at the seaside.
Took a train to Goetborg, Sweden to go to Liesberg. Then the 2-hr ferry to Frederikshavn where I rented a car and went to
Fårup Sommerland and then drove to Copenhagen, where I spent three days visiting the city including seeing the Thorvaldsens Museum to see the original Christus statue and also the church with the Christus statue and all of the apostles. I also took a canal tour, visited the twisty church near the canal and Christinaia which is a hippie village. I went to 3 theme parks near Copenhagen: Tivoli, Bakken and BonBonland.
From Copenhagen, I flew back to Dusseldorf and drove to Phantasialand, then flew that evening to Alicante, Spain and went to Terra Mitica and saw a castle and the beach. I then drove to Barcelona and there was a small amusement park that I went to that no longer exists. I also saw a lot of the city. Then I drove to Port Aventura an hour or so south.
I flew into Rome and did the small EUR park and then to Paris for Park Asterix and Disney. Then home.