Kiefer Sutherland, Chris O'Donnell, and Oliver Platt all endured six weeks of fencing and riding lessons. Charlie Sheen missed out on all of this, as he was then embroiled in the filming of Hot Shots! Part Deux (1993).
The dungeon scenes were filmed at Seegrotte, Austria, an old mine which was flooded early in 1900s due to an underground water source and was later used by the Nazi's during World War II to conduct military research. The site is now open to the public and famous for its underground lake. The scene decoration of one of the prison cells, as well as the dragon-head boat are still kept intact at Seegrotte and can be visited.