Okay, I thought, I'll put a lever in the center of this dungeon that will change the axis of the dungeon's rotation.
So, I'm curious what was your biggest DMing screw up was. Please. Be honest, this is a safe place . . .
Update: Thanks for the comments so far. I thought I'd add this pic to demonstrate what should have happened if I hadn't pretended it hadn't. The water is pouring out the opening, down the hallway there, and off into the rest of the dungeon: