9 Secret Levels You Missed In This Decade's Biggest Video Games

9. DOOM & DOOM II's Classic Levels - DOOM (2016)

Looking like some bizarre glitch if you happened to stumble upon one of these, 2016's DOOM actually includes a host of both the original game's levels and some of DOOM II's, rendered in all their blocky 90s glory.

To access them you'll need to check the above video as each one is in a specific place, but brilliantly, they play as a mix of the old and new.

Enemy placement matches where they were in the originals - replete with weapon loadouts and restricted movement - but your own firearms, animations, kills and the enemy models themselves are carried across from the modern version.

It's the perfect way to tease how a remake of the original games might look, and yes, Hangar is still a LOT of fun.