Don't know if this relates to main quest but I found a large unmarked bunker complex entrance via sewer systemnot marked on the map its a unmarked location it has a lot of terminals inside with lore involving Slocum Joe as a U.S.spy service and chinese hen geu stealth armor and a machine named P.A.M. there are a few synth enemies a fusion core and a us covert op code book

There are loads of terminals loot and a few cryo mines on the floor and it all ends in a terminal that is inaccessible that unlock a very heavy duty vault door with 2 sets of hazmat gear sitting on a table by it

Anyone know how to open this door is this in any quests you've found?

Its old railroad HQ it gets unlocked via their story line.(you get a quest to retrive something from there after joining them)