I've had many many dreams about the same mansion for over a year now. Each dream, I meet different people who usually wind up being spirits trapped within the house. I've never visited or seen this mansion ever before, though it's constructed in a Victorian style with two large spiral staircases right off the foyer. It has multiple secret passages that I've discovered over the course of the dreams, and some of the rooms I've discovered fill me with a sense of dread and I get flashes of horrible murders being committed there. The dreams are never the same, but the location is. What does it mean?
Constant dreams about houses, dwellings etc can be indicative about how the dreamer may be feeling about their own sense of 'place'. It's an inbuilt need within the human psyche to have a sense of place and for that place to be one that is structured, primarily for security and for acceptance by others who share that space.
Could it be that there's something in your life in which you are not finding that security? It could be anywhere where there is a structure ie., school, work, home environment. Are you witnessing things around you, in your waking life, that are causing you concern to do with others? I refer to the part where you say that "horrible murders being committed there". Are you seeing others being treated badly/unfairly?
That "mansion" whatever it might be symbolic of, might not be just the place for you. Or else you can work towards 'owning' more your sense of place and work towards making your personal environment more secure for yourself. :)