|Designer / calculations||Ton van de Ven|
|Onsite construction||Bouw- en aannemingsbedrijf Merkx B.V.|
|Animatronics||Amount not exactly known|
in 1966, Efteling opened Indische Waterlelies in the Fairytale Forest. This was the parks first animatronic-show, and became a huge succes, prompting the park to want an even bigger version. This would become the second indoor attraction (Stoomcarrousel was the first) outside of the Fairytale Forest, and pave the way for all future expansions.
The idea to make it a Haunted attraction was thrown around very quickly, and Efteling Designer Ton van de Ven got to work on the attraction, under supervision of Anton Pieck. Somewhere in development, the decision was made to turn it into a theater show, dubbed the Ghost-Opera. The original plans showed two theaters and a elaborate themed area around it, this got scaled down to one theater and a small scale area in front of the castle. 
The ride is located in the "Anderrijk" area of the park, roughly translating to "Different Realm".
Spookslot translates to Ghost castle, but Haunted Castle is the more accurate translation.
The attraction is themed as the ruin of a Celtic castle. The story of the ride tells us that this was the former castle of the fourth viscount of Capelle van Kaatsheuvel, who collected fairytales and story from around the world. The Witch Visculamia was his arch-nemesis, wanting to steal his story's. On one faithful day, the witch disguised itself as a young virgin, trying to make her way into the castle. But she was busted by the castle's gardener. She was sentenced to the stake in the east wing of the castle by the three judges of the duchy. With her final words, she screamed out a curse, dooming the king to never find his last story: his daughter Esmeralda.