Villa Volta is a in Fairy Realm at Efteling. While it's not a "must do," it is also recommended.
Enter the house of Hugo the Goat Rider (don't ask), head of the criminal gang De Bokkenrijders and prepare to discover the curse that was lain upon him when he stole holy treasure. This first Mad House ride in the world throws up nothing particularly impressive in terms of visuals, but showcases one of the best soundtracks from any theme park ride. It also begins with a lengthy pre-show with a real looking animatronic, that will be completely meaningless to anyone who doesn't speak Dutch. Nonetheless, this is a must-do ride.