This is something I sometimes do, if I'm having a vivid lucid dream, and I want to play around with it.

First, I imagine some kind of hallway or big room, it usually ends up being without doors. Then, I visualise and "spawn" a door someplace on the wall. If it's not working, it helps to trace a frame on the wall with my finger, and a door will appear.

Now, the fun is to open this door, and not willingly not control what will be behind the door. This is a fun way to "randomise" my lucid dream, and explore my own mind, so to say.

I might find an ordinary bathroom. I pay attention to the details, maybe walk around in there a little, then walk out and close the door. When I open it again, there will be something else behind it. Maybe a closet. Maybe a portal to another world.

Do any of you guys do similar things? You should try it, if you can remember to!