March 2025?

I am in the process of planning our honeymoon. We love sightseeing as well as theme parks so I decided we would do 3 days in London and 5 days in Paris (to also do Disneyland there). The problem is I don’t know what the 3rd destination should be? We don’t want to spend too much more but we do was to do a 14 day trip. Where can I go that’s close by to london and Paris and I can spend 5-6 days there and wouldn’t get bored? Thank you!