I've done a meditation where you sit open eyed and visualize something within the space.
It was cool. Sort of like a hazy projection over the visual field. Normally when I visualize something with my minds eye it is on a black background. When the visualization ends my visual field snaps back to reality.
Visual hallucinations due to mental illness are uncommon but not unknown. I'd be reluctant to dismiss the idea that someone on earth can and does do that. I'm pretty far down the visualization direction myself.