Agents of STRIKE
The Hollow is ARMOR’s HQ. It is also where ARMOR’s multiversal portal device (codenamed “The Holepunch”) is located.
The Hollow is actually in an interstitial space, literally off the grid by virtue of occupying a space between spaces. It’s not a true pocket dimension, but existing inside folded space by using a variation of Kree space-fold technology thanks to the work of Dr. Jane Foster.
Physically, the Hollow is deep underground in Eurajoki, Finland. ARMOR used the Onkalo Nuclear Fuel Repository Project as a cover to build the foundation for the Hollow in the most geologically stable place on Earth, because it was absolutely essential that there were zero geological disruptions during construction prior to activation. Now that the Hollow is stabilized, it doesn’t really matter where it is, because you can’t physically travel there.
The Hollow can only only be accessed by specifically designed gates (derived from Kree fold-gates), which are connected to every major ARMOR base and the Chariot mobile platform. Each gate only works in one direction at a time (can’t go in through an out door), and the polarity has to be manually reversed on one side or the other to change it. Each location connected to the Hollow has its own unique paired gate (the fold-gates use quantum entanglement to function) so the Hollow serves as a sort of “transit hub” for ARMOR to move around the globe quickly and without being noticed.
The Holepunch is the real core of the facility, however. Using a slurry of tech acquired from the Kree, Reed Richards, and other sources, ARMOR has created their own multiversal gate that allows us to travel the multiverse on our own. The Holepunch’s technology and science is enormously complicated and beyond the scope of this document.