When walking outside, I sometimes focus mostly on all the sounds around me and try to differentiate them all, building a 3D auditory map of my surroundings.
Passive Thought Observation
Before going to sleep, I close my eyes and observe my thoughts. I can see them appearing, morphing and vanishing like ever-changing clouds on a cinema screen.
Controlled Fly-through Mental Exploration
I create a mental 3D scene and imagine flying around a room, going under tables, raising close the ceiling, as the scene angles and details are changing. Another scene I like is to imagine slowly taking-off with a jet pack and feeling my body lifting from the ground and looking at the changing perspective of the landscape as I go higher. I also imagine flying above a wheat field, twisting and flipping in the air, then flying over a cliff — all with images so vivid it looks like a camera on a plane.
Natural Complexity Awareness
I look at the fractal structure of branches, the multiple layers of moving clouds at different altitudes, etc. I also imagine how the landscape where I stand would of there were no roads, no buildings and nothing built by people.
I sometimes mentally zoom out from me and see my street, my town, my country, my continent, the Earth and keep zooming out to the solar system and galaxy level. At that moment, I have the very clear feeling of being on the surface of a planet, in space, way off the center of our galaxy. I also do the opposite and imagine the atomic structure of the floor or my body, being made mostly of empty space between the nucleus of the atoms and their orbiting electrons.
What mental games do you play?