This one has got me really stumped! I'm thinking it has to be somewhere in Arizona, like secluded mountains in the Lake Havasu region.

It just cannot be in NCR territory because the NCR govt. would certainly have found it before Elijah and Dog would have had to drag you through the Mojave outpost to get to NCR territory so I think we can safely rule out California.

The starting point of the DLC is the Abandoned BoS Bunker which is located on the east side of the mojave map on the edge of the Colorado which is the border of Legion territory so it's gotta be to the east or northeast which puts it squarely in Legion turf but how come neither Caesar or his Legion seems to know anything about it or have tried to get into it?

Maybe since Caesar and the Legion are fundamentally against advanced Pre-War technology that they just left it alone but Ulysses for sure has seen it and knows its location as he is the one who first told Elijah about it?

What do you guys think??

In my head I've always pictured it somewhere south/south-east of New Vegas. Somewhere out of the way and remote (and barren) that rarely sees visitors aside from the treasure hunters that go after The Madre.

A lot of people always say it must be in the Sierra Madre mountain range, but I don't believe thats the case. Thats way too deep into NCR territory. It might share the name of the mountains, but not the geographic location.

So yes I agree, somewhere south in the Arizona area would make sense.

Edit: Although its worth mentioning that Arizona is also under Legion control. Since Flagstaff is their Capital. But it may simply be a part of Arizona which The Legion strays away from.

Yeah good point actually, southwest Arizona would fit as the Sierra Madre Occidental mountain range in Mexico runs north to that point and that part of Arizona is probably not strictly under Legion control as it is pretty far from Flagstaff.

I am thinking it is right on the border between Arizona and Mexico. I believe the Sierra Madre Occidental mountain chain starts around there. Maybe in 2077 that area might have been part of the States.

https://en.wikipedia.org/wiki/Sierra_Madre_Occidental