Moscow Necropolis

"Deep down deep down, many hands many demands. Run? Can't! Fight? Kill! Hunt? Institute! Long life the Necropolis!" 
-weird guy who asked me for shrooms 
The Moscow Necropolis is a large, underground city located beneath the city of Moscow. Its foundations were first laid after the destruction of Moscow in the 2050s, during the height of the 2nd Russian Civil War's second phase. As a result of the city's leveling by both the Lavender and Chamomile factions, the administration attempted to both ensure the city's future safety in case of another attack, and draw corporations back with promises of money. 
As a result, the remnants of the Russian Government promised every company that returned a certain stake in the city's future affairs, as well as money equivalent to the amount of floor space built, with that number tripling for underground bunker space. This lead to both the city's current state as an oligarchic republic, and the construction of the bunker network that would one day become the Moscow Necropolis. 
Also around the time of the city's reconstruction, the newly formed Moscow Institute of Magic took over responsibility of Russia's underworld territories from the White Cross. Though once a strict organization, the emergence of the When Day Breaks Grand Rift Zone in Norilsk stole away much of the MIM's resources, forcing it into taking a lassis-faire approach to its rule. This resulted in a large influx of supernatural business. However, due to the rhabdophobic nature of Russia at the time, many of these new mages followed the pre-existing mage population underground, literally. Various organizations, cults, and businesses began carving deep into the Muscovite rock, forming the man-made cave system that stretches below Moscow. 
The Moscow Necropolis that exists today still retains many of these old foundations. It is a den of crime and villainy, but also home to over a million mages, nonmages, and extradimensionals, which participate in a vibrant underground ecosystem, untouched by authority.