When we go abroad as a family we generally just visit the local areas and later on (3-4 days in) we usually visit the larger towns away from where we're staying, nothing is ever planned before we go.
We generally go to somewhere further out in the morning, have an early lunch, explore the area and visit many shops in which we very rarely buy anything. After we've done our exploring for the day we go back to where we stay, have a quick shower and go out for a meal.
It's just finding what you like, we're a family so we can't do what we want as individuals but we still enjoy it greatly.
I should imagine its much different being only you and your partner but do things you wouldn't normally.
Look at off road buggying, paragliding, wildlife reserves, water parks.. Things that you always look at and think "I'd love to try that"
Sorry for the babbling but I hope it helped