OK, you asked for it...
During the cold war, the government contracted with AT&T to develop a cross-country communications system in the event of world war and traditional phone and other communications systems went down.
So, a communications systems was developed and is commonly known as the "AT&T long line" system. You may have seen microwave relay towers in your travels. These are the towers with the big cones on top that point in 4 different directions. Those are part of the system.
Anyway, the microwave and other signals needed cleaning and amplification every 50 miles or so (which is the increment where you find the towers). If the station that did this service was in an area prone to be the recipient of a nuke, they made a redundant site in a hardened facility. That's what this site was.
With the end of the cold war (and the common use of satellites), the site was decommissioned. It was cleaned out of the communications equipment and shut down (including asbestos abatement and other nasty stuff removed).
It's underground and made to withstand a nuke blast as close as 5 miles. It has all the powered blast doors, EMP protection... The exterior is wrapped in copper coils.
Inside there's around 16,000 sq/ft.
There's:
NBC filtration
HVAC
2 generators (150KW each)
rest room
decontamination shower
Kitchen (or medical facility if needed)
A conference Room
sewer plant
2 deep water wells
more electric than you can imagine... 8400v outside and a pile of transformers inside.
24v emergency power
We (my partner and I) did some work on it including re-doing the bathroom, kitchen, conference room, fired the sewer, 24v ele. back up, new lights, drywall work, painting...
For now, it's not really being used. We both have some stuff in it but most of it is used by the kids as a playground on bad weather days.