DOOM- Lever Location in Titan's Realm (Level 10)

How to unlock the classic playable level Phobos Anomaly (E1M8) from DOOM in the 2016 version of DOOM. This easter egg is found in the tenth level of Doom on the level Titan's Realm. 1. Find a hidden lever and pull it. A retro chime will sound. 2. After the chime, a secret door will open somewhere in the level. 3. Find the door to explore a classic DOOM stage with original low-resolution (with bumped up graphics) wall textures and layouts.