Whilst taking the train from London to Östersund (northern Sweden), which I do quite frequently, I usually plan it so that I get a free day in Copenhagen. It looks like this:
London -> Brussels -> Cologne -> (overnight) Copenhagen -> day of sightseeing in Copenhagen -> Malmö -> (overnight) Stockholm -> Östersund
Anyway, I'm getting pretty bored of Copenhagen, so I was wondering if it was possible to rearrange it in some way so that I could visit e.g. Berlin or somewhere instead, taking the same amount of days of travel (i.e. 2 overnight segments).