Mine was the drain hexadus.
I don't know about you guys but hexadus is easily the slipperiest drain I have ever explored. on top of that there is this big puddle at the start of the drain that u have to wall run or do the splits or what ever to get past.
I walked through it cause I couldn't be fucked. (;
Man cannot discover new oceans unless he has the courage to lose sight of the shore.