During Death's Door - the fifth mission in Horizon: Forbidden West - you'll encounter a locked door which requires a code.
If you want to fully explore the Latopolis facility, then you must unlock the door by inputting the correct four digit code.
Once the door is opened, you'll be a step closer to completing the mission and, hopefully, finding a backup of GAIA.
Below you'll find the code for the bunker door, along with how to find it, so you don't get stuck in an abandoned lab.
Code for locked bunker door in Death's Door mission for Horizon Forbidden West
The code for the locked door during the Death's Door mission of Horizon: Forbidden West is 7482.
To find this code, you need to head to the southern section of the room where the locked bunker door is located. There you'll find a collectible, which, when read, contains the four digit number you've been looking for.
Good luck in Horizon: Forbidden West!