A Quokka Dreeds its Weird

I am creating a giant, monstrous, bizarre house for something I'm writing. Without getting too in-depth regarding the premise, the house itself is very loosely inspired by the Winchester House, but is much weirder: a gigantic and somewhat hideous edifice largely constructed of gray rock and plonked down in the Hollywood Hills.

I need suggestions for weird features that might be amusing to write/read about, that could play into the plot or simply alarm the heroine.

Parameters: most of the house was constructed around the turn of the century, so no modern gadgets. Though there could be ill-fitting interfaces between the original structure and modern conveniences that were added later. The builder was enormously wealthy and extremely strange. Think surreal and creepy, like a Gothic novel on acid.

I already have staircases leading into solid walls, doors opening on to solid walls, secret passageways, trap doors, trompe l'oeil, clawed furniture, disquieting paintings, rooms with no entrances, nightengale floors, and areas that can only be accessed by flight.

Note: If you think you know what this is, yes, it's that one.

ETA: The house is not magical. Just weird.