So, I was lying down to try and take a quick power nap. I didn't end up falling asleep--I guess I still have some caffeine in my system--but I was still able to let my mind rest and relax a bit. After the first few minutes, a potential solution for the bug I've been trying to fix for my game popped into my head; after that, though, things started to get interesting.
I started having this... I guess it was a closed-eye hallucination, or some vivid hypnogogic impression close to one. At first, it was just these monochromatic wireframes of some items in my apartment--a bottle, a refrigerator, a crockpot--then it shifted to this powerful image of a colossal spiral staircase. It seemed to be carved out of some cave system, just spiralling endlessly down and down and down and down. There was a central pillar that kept fading in and out; while it was faded out, I tried looking down, but all I could see was darkness--the bottom (if there was one) was far, far out of sight.
After several minutes of just wandering downward, I jolted up out of my bed and back to reality, then just sat there digesting it for a minute or two. And now I'm here typing this up, heh.