Mountain Chiliad IAA Bunker is a 1.7-kilometer tunnel, still under construction in the bowels of Mount Chiliad, that you have to cross to get to the IAA bunker. For the best game and start at night. And yes, in the dark.
Modifications such as Menyoo, HeapAdjuster, Simple Trainer, Packfile Limit Adjuster are required to work. Enjoy the game!