Manzanares el Real castle was modified for the film with the digging of a moat. The discovery of a bone during the digging halted the filming for a while until it was confirmed to be merely that of a dog. It is from this castle that the Duke of Beaufort is rescued.
The castle is also the scene of the film’s climax, with the musketeers hi-jacking a hot air balloon and using it to enter the castle for the final showdown, with swordfights all over and around the battlements and cloisters.