New Den? Or Old forgotten den?

These are some pictures I took of this den I have never seen. I hope you comment on what it is and help me find out about it!

The front door of the den.

Sorry about the text! This is the room after the door.

Dead plants. Very 1890's.

These are the pictures in the den. Pretty old huh?

Me up the staircase.

In a room.

Me and my friends.

Last pic. This is up the other staircase.

Please comment and help me find out how someone can get this den!