If you're willing to make a little trek into the woods of Patapsco Valley State Park, you can explore the ruins of St. Mary's College, including what's left of the campus chapel. People call it the "Hell House," but we think of it as the Beetlejuice Temple, since some industrious graffiti artists have transformed it with a little paint and a lot of imagination.
From SECRET DC: "The old St. Mary’s ruins are located near Ilchester and can be easily reached by hopping on Buzzard Rock trail off of Hilltop Road to get a bird’s eye view of the property. You can also head into the ruins by walking back the railroad bridge near where Illcester Road meets River Road. There are steps hidden on the south side of the railroad bridge that will take you up to the ruins."