I saw people doing this (for no specific reason) and came an idea into my mind: what about making them a joke with this "tour"?

Let's say you are visited by some old friends and they never saw your house. As usual they expect you to make them the "house tour", showing each corner of the house, explaining how was built etc and bullshit like that.

But from the whole house, especially you are missing a single room. It could be an empty room, a closet or whatever space, but with a door and you do not open it. When you come close to that door, you just move away and try to evade the answer if they insist to see that room. Will be even more interesting to play an audio record in that room, with a creepy sound like torturing somebody or any other sound you think will bring more attention to the visitor and activated remotely by you when you are close to that door. Nothing scary, just more mistery.

Prepare previously that room with a video camera that start recording the door at any movement.

Then later, just relax with the visitors on the sofa in the living room, talking, drinking etc. You will see that their curiosity for that room is extreme and suddenly will ask to go to the bathroom. For sure they do not go to the bathroom, but to see that room.

And voila! Once they open the door, will see an empty room (camera is hidden). Nothing in there. But will be nice if you have somebody else taking the video of them entering the room (without permission) and put it on a DVD or a USB stick or something. Then when is about to leave, you just hand over the DVD/USB with the recording of them enetering the room and saying: "Thanks for violating my privacy, my friend, I was trusting you."

Seeing their face will be so fun, paramount.