I know this sounds impossible because rainbows move relative to where you are, but I actually drove through the end of a rainbow once... not on STJ, I don't remember where. Whoever went through it ahead of me must've gotten the pot o' gold!
DH and I saw the coolest thing once in the Grand Canyon -- the full arc of the rainbow, with both ends visible and looking like they originated from the sides of the canyon. Awe-inspiring!