 Scenes in the cave were filmed in an abandoned mine in Deadwood, where the crew was allowed to film.While shooting scenes in the cave that required the actors to use guns, the sounds reverberating from the fired ammunition would sometimes cause parts of the cave's ceiling to break off, which made some of the cast and crew members nervous while working on location.Other problems arose while filming in the mine, as the air became very stale to the point where the crew had to pump air into the cave; the problem was never completely solved due to improper equipment.