Military Base. The place is a great challenge no denying that.
The Elite Former Commandos though seemed like an abuse of nature and too overboard for such an early dungeon level.
Lost one time there recently, cause I encountered one with a freaking napalm launcher.
He did die in the end cause I got near him, but not before exploding us both and filling the whole place with lava without leaving a single exit path.
Couldn't escape the lava, so I naturally died there. Was an impatience game so no medpacks with me...
The other elites in there, are too random as well, so someone would need to be extremely careful to survive it in high difficulties, the only way avoiding all the shots all-together, not that easy with so many elites.
Those unique and exotic weapons the enemies wield at barely level 7, are just too powerful in some games.
And I think it's the first time excluding boss fights, that doomguy can not get the weapon the enemies wield, which I found extremely unfair.