...Screw it, I've got time and if jacobplm doesn't like my description of our base then he doesn't have to take it.
An outgrowth of the original Two Step Fortresses used to safeguard border populations during the War, Long Term Fortresses were all built to a generally standard design. A central 'keep' serves as the heart of the stronghold, extending deep into the ground and being the armored core that keeps the population and living systems safe. Different levels might have different complexes branching off, ranging from workshop centers to empty space for children to claim and play in. The power source that feeds the entire structure is a VK Power Pack housed in the bottom floor, and is very well secured against even things that can burrow.
Surface features are more variable, as the local terrain has an inordinate impact on what would be allowable, but each Fortress was built to be able to serve a plethora of functions after the Union fell. Large, reinforced elevators could be used for moving aircraft or vehicles up or down, as well as limiting the ability of any attacker to simply banzai the actual entrance into the Fortress.
Argleblargle-13 (I think we were 13 at least) was one of the last Fortresses to come into operation, and because of that it was never fully outfitted with weaponry or manufacturing. It has also been fully locked down for the last hundred years, and as such it isn't well known what the aboveground facilities are, let alone if any could even remain functional at this date.