Interestingly, in the vicinity of Blue Ridge Summit, PA, there is a vast, sprawling underground bunker run by the military which is supposedly some sort of electronic nerve center and command post. The installation is maintained by nearby Fort Richie, MD, and is also often called “Raven Rock,” “Site R,” and “The Underground Pentagon.”
Located 650 feet down within solid limestone, the facility reportedly covers 260,000 sq. ft. and sprawls out over 716 acres, encompassing five different subterranean buildings. The high security base allegedly is connected to Camp David via tunnel, and is said to have vast warrens of interconnected tunnels, passageways, and caverns, most of which are top secret. Taking this into consideration, it has been speculated that some of the weird stories of underground humanoids and creatures could have some link with this mysterious network of military underground tunnels and buildings, or that the installation is involved with some sort of top secret research that could have something to do with the phenomena.
- https://mysteriousuniverse.org/2015/06/strange-mysteries-of-the-appalachian-mountains/
An arcology city built into a mountain, excluding the population of the now-sprawling Hagerstown. The arco is a center of Unionist support, while Blue Ridge tends to be critical of the measure.
There are rumors that due to cave-ins in remote and abandoned locales of the structure, the Maintenance Interstices are now experiencing incursions of Blue Delta-Homunculus ("Feral," "Ghoul"). But these reports are by sub-citizen level homunculi, not to be believed. Those Deltas are shifty anyway, always paranoid about something. And those piles of bones picked clean? Urban legend. That breath condensing on the back of my neck? Oh.
More info:
https://en.wikipedia.org/wiki/Raven_Rock_Mountain_Complex