Ok, I know mobs can spawn in and under it, and I know the first drop of TNT blows the crap out of the ladders, but at the end of the day it's designed to do one thing...make a very big hole in the ground.

Instructions:

Go through door
Climb ladder
Press buttons one after the other (wait for the last drop to blow before moving on to the next button)
Do NOT accidentally miss a button

Owing to the self-damage issue, you may question the "100% complete" statement. However, only a masochist would ever attempt to reload this thing...just rip it out and place another if you want to make another hole.

This is my first schematic/submission so constructive criticism is welcome.