Fort Hecate is nearly a century old and is one of the largest and most important military installations of the Lunar Free States. Like the Kingdoms of Scandinavia and New Themyscira, the Lunar Free States enjoy a friendly autonomous relationship with the Atlantic Federation, such that many of the rivals of the Federation see no difference between them. The LFS contains the 3rd largest human population in the Solar system, after Earth (obviously) and Huo Hsing/Mars. It vigorously maintains a highly liberal and demi-socialist economy, and is known for its fair and legal treatment of sentient beings that arent human, clones, and other areas of social progress. To this end, the LFS have a number of enemies, mostly along ideological lines, as not many terrestrial nations have resource or territory concerns with or on the moon. It still behooves Luna to have it's own (largely automated) Self Defense Force. The Lunar Free State Self Defense Force (LFSSDF) is known for fielding 'Caspers' or fully automated 'ghost ships' in its small defense fleet, and large numbers of drone fighters, drone mecha, and non-auton style robot units for ground work.
The Fortress Hecate
The Fortress Hecate was designed and built by engineers and contractors from the New Hanseatic League, and looks the part. Like an iceberg, the fortress projecting from the lunar surface on represents a tenth of the total structure. From the surface, there are a pair of towers, one for communications, the other for sighting and observation. There are a cluster of antenna between these towers, and these can be used for targeting and triangulation for the guns of the fortress. Hecate has four large cannon turrets, named Hag, Hexe, Jinx, and Scyilla. These turrets set at two different elevations, with Hag and Jinx sitting above Hexe and Scylla. There is further superstructure around these turrets, armored walls and bunkers where soldiers and even mecha can shelter. The entire fortress is designed for fight foes both on the surface of the moon, and in orbit above it. From the sky, it is laid out like a massive warship sitting on the surface of the planet, bereft of ocean or current.
Entering Hecate can be done a number of ways. It has a pair of landing pads and is functionally a small spaceport. Given the low lunar gravity, it is not hard for ships to land and take off under their own power so their are no launch assist devices or magnetic launchers. Landing at a pad is no different from landing at any other military base, and personnel access the facility through hanger doors on the side of the 'hull' where elevators can lower aerospace craft and mecha to the armored interior of the base. There are eight such doors, four on each side. The second option is to access the base through the Deep Rail system. The Deep Rail connects a number of important lunar sites, and is half a kilometer under the lunar surface. It was bored out by a number of boring machines, and a lunar hyperloop network was installed. Most troops stationed at Hecate arrive via the Toob, as it is called.
The Upper Levels
The Upper Levels of Hecate are composed of massive hangars that are built geofront style under the main fortress. They are protected by reinforced ferroconcrete walls that are dozens of meters thick and impervious to all but the most apocalyptic weaponry. Inside the hangar deck there are facilities for holding and tended a full mech division, two aerospace wings, and a conventional infantry division.
B4 separates the hangar from the rest of the base below. Should Hecate be breached, and the hangars broken open, Bulkhead 4 is designed to hold out for as long as possible allowing the base personnel to escape through the Toob, and to activate seld destruct charges to prevent Hecate from being taken. The bulkhead is a three meter thick slab of battleship armor grade material and has the ability to activate an energized phase shield. The realistic main purpose of B4 is to protect the rest of the base from a military accident in the hangar like a power plant explosion or magazine explosion.
Operations and Command
The admin and command center of Hecate, the Op/Command level houses the war rooms, planning systems, and administrative personnel who coordinate military operations on Luna. It is also the region hub of the Autonomous Defense Network of the LFSSDF drone forces.
The Rec Center
The Rec Center houses the recreation facilities of Hecate, including available shopping and entertainment venues, and if removed from the confines of a massive military base, it would not be out of place inside a major arcology center, serving the recreational needs of the residents. Up to 12,000 people occupy Hecate, and the six decks of the Rec Center offer enough space and amenities for a larger capacity.
B3 separates the residential and hospital sections of Hecate. It is made of the same grade material as B4 but is not phase or energy shielded.
Residential and Hospital
Under the protection of Bulk3, the staff and crew of Hecate have their personal quarters, where they spend their 6 month deployments. The staff of the Rec Center, and quarters for the marines, pilots, and other fighting men and women are here. Elevators and spiral looping mini 'toobs' connect this level to the rest of the base. As many as 20,000 people can reside in the residential sector, almost a half mile underground.
The Hospital sector is a full military hospital, and treats all soldiers of the LFSSDF, not just those deployed to Hecate. It is considered a premiere lunar facility.
The Toob Head is also in the residential sector, and is the main access point for the rest of the Moon. The Toob is serviced by Magnetic Rail trams that run the tubes at close to 450mph. There is no wind resistance as the tunnels are not pressurized, allowing for this high speed to maintained easily by relatively small electric motors. Hecate is NOT a Toob junction or hub, but rather an End of the Line destination. It is serviced by another hub, where security makes sure that no non-authorized visitors or passengers end up going to Hecate.
Bulkhead 2 protects the environmental and power supply systems for the entire base. It is half the thickness of the previous bulkheads and is made of industrial grade rather than military grade materials.
Mechanical houses the environmental systems and power supply systems of Hecate, it is a mechanical deck with few human amenities, and most personnel who work in Mechanical do so in hostile environment suits. Waste and water recycling are also handed in mechanical. Processed waste is either sent via container in the Toob, or is fed to an incinerator. Aside from water and O2, Hecate is not self sufficient in any means, and doesn't have any sort of hydroponics or food production capabilities.
Bulkhead 1 matches Bulkhead 2 in schematic design.
The Power section of Hecate is over a mile and a half beneath the surface, and is comprised of four toroidal fusion reactors and a pair of dimensional reactors. These provide main and auxilliary power to the base. This is also a mechanical deck, and crews are required to wear hostile environment gear.
There are rumors of a Bulkhead 0, and that there is more to Hecate under it. Each rumor is more fantastical than the last. THe more garden variety rumors involve secret military operations and inhuman scientific and medical experiments, to a military prison for sociopaths and rogue supersoldiers. The most fanciful versions include alien vaults full of alien space treasure, access points to a Hollow Moon, the wreck of a pre-human space ship derelict, to the corpse of a teratomorph or some other Cosmic Horror.
The Point and Inspiration
Fortress Hecate is a large, very important, and likely very mundane military installation on the Moon. It is a big and busy place for Lunar Space Progressives to make sure Earthlings and their mudball religious orthodoxy and regressive conservatism stay off of the Moon. From the surface, the fortress looks like a battleship, which tends to draw the eye, where the surface superstructure is made of armor and materials that are nearly impervious to existing weapons. A Federation Battlestar could show up and start laying into Hecate with it's kiloton yield higgs cannons and just ring the fortress like a bell. Hecate would return fire with it's own Hanseatic made Higgs cannons, and prove that the armor of the battlestars is much much thinner than their own.
The inspiration for Hecate is Fort Drum, in the Philippines. The military took an island, a rough outcropping of rock in a bay, and turned it into a fortress, that was shaped largely like a warship, and fitted it with gun turrets that were modeled after a battleship. Thus, Fort Drum looked like a stumpy warship sitting in the harbor. It proved massively difficult for the Japanese to take in WWII and survived MONTHs of being shelled by artillery and warships, and was only starved out at the last, after they ran out of ammo and the other island forts were taken. Likewise, Hecate, and its ability to coordinate and control the lunar drone forces would remain in action for a protracted period of time, more than long enough for the Lunar Free States allies to become involved in any such conflict.