dude, i've gotten lost in the woods behind my house, knowing i'd never make it out alive... i walked/stumbled/crawled for hours, looking for the house...
my back yard was a partially wooded, fenced half acre...
i was fishing at the bottom of a dam, the river side, and the entire river flushed like a toilet. all the water went down the drain. that was fucking trippy...
same spot, different time, it looked to me like the water was higher than the rocks sticking out of it. that is the best explanation i can give you, weirdest optical illusion i've ever experienced.
another time, i got the yawns and decided to lie down. after successfully making it into bed after god-knows-how-many attempts, i was overjoyed at the amazingly incredible soft cloud that was my bed. soooooooooo comfortable! so as i'm being caressed by my super mega soft and floaty bed, eyes closed, i daze out into a kind of trance, and hear all these amazing alien sounds! i'd never heard anything like it, so effervescent and distant, teasing me, surrounding me, getting closer, fading back... i was so immersed in this heavenly state that space and time seemed to either not exist, or be something entirely different from what i imagine reality to be. all these soft and playful sounds, with a pattern and rhythm that i was just starting to be able to understand WHUMP!!!!! (amplify by ten billion).
all the sounds were gone, like as soon as these beings discovered i could understand them, they threw me back to reality. that was my first and most intense audible trip. the loud sound felt like the universe collapsing in a split second. it freaked me the fuck out for days...