My oxygen tanks bumped the low ceiling of the narrow tunnel. My sigh of relief bubbled up towards the ceiling when the cave opened up again. I shined my light around and was surprised by a gold shimmer in the darkness. I swam closer, squinting against the yellow shine. Whatever it was reminded me of a golden ziggurat. I followed it up and found myself in a small lake inside a cave. On a whim, I took my respirator off and found there was oxygen enough to breathe. The strange structure’s shrinking tiers reached up towards the cave’s dark ceiling.