Trying to find title of a horror movie?

When I was a kid I woke up one night and Cinemax was showing this moving that I only caught part of. It involved a very large house/castle that had a long spiral staircase that went into a deep basement. In the basement was a deep well with a monster kept prisoner in it. I vaguely recall it ending with an explosion in an attempt to kill it. Does this ring a bell for anyone? This was early 1990s maybe.