Primary Excavation: Artifact Dig

Primary Excavation: Artifact Dig is the twenty-seventh and final level of Doom 3. The player must defeat the fourth and final boss, the Cyberdemon, in order to seal the Hell portal. An exploratory player may find the hidden "id Software" PDA, containing messages from several id Software employees.

Easter Egg
(Note: This Easter Egg can only be found using the God Mode cheat.) When facing the Cyberdemon, enter the god mode cheat and jump into the "hellhole" in the center. Crawl all the way down until it ends. At the very end, there should be an ammo pack, a health pack, or some other beneficial item. Different things have been found, as they seem to appear at random. Another cool little tidbit is while all the way down in the very pit of the "hellhole", god mode can be turned off and the player won't get hurt, although you will die if you try to get out without the god mode on. Another interesting thing is that while battling the Cyberdemon, you can put noclip mode on, go through the left wall, and keep going. If you went far enough, you will be in the beginning of Hell and the area where the final scene takes place (before the video of the rescue) is there as well.