If your trip to Opperdoes is all locked in but your travel itinerary is a bit on the empty side, let us give you a few hints and tips.Not far from the heart of the city, Radboud Castle is one sight you might like to add to your to-do list. If you still have room on that itinerary, Vlietlanden Golfbaan and Stoommachine Museum will keep you amused as well.