Once you’ve climbed the VNC Tower and completed the Broadcast story quest in Dying Light 2 Stay Human, you can then use one of the elevators on the ground floor of the VNC Tower. Take that elevator to the VNC Tower roof. Turn left when you exit the elevator and step out onto the solar panel sticking out of the west side of the roof. Walk to the end of the solar panel, turn back toward the building, and look down to find a broken window in the wall. Drop down to this opening and you’ll find yourself in an office containing a loot crate, an Inhibitor Container, and a safe.
The VNC Tower safe code note is on the desk in the southeast corner of the office. Read it in the Collectables section of your inventory and you’ll see that it says, “IF U 555, THEN I’M…”, which is the easiest safe code ever if you’re a fan of Slipknot. If you’re not a fan of Slipknot, then this is the first part of a line from the song The Heretic Anthem. The complete line is “If you’re 555, then I’m 666.” So, the VNC Tower safe code is 666. Enter 6 – 6 – 6 into the safe to open it and collect one of the red ducks required to unlock the Doom easter egg.