Located in the sleepy Belgian town of Cheratte at the very heart of Europe, this massive abandoned mine complex combines an ominous facade with a dignified title, much like Baron Destro, to form the perfect location for some old-fashioned continental terrorism. It offers all the amenities your villainous soul could desire, including a Gate of Evil, a mansion-like exterior, a looming Dark Tower, industrial equipment that could easily double as torture devices, and vast underground caverns over 1,300 feet deep for doomsday device/giant-mech-with-your-own-face parking. The fact that it features plenty of multi-platformed, elevated corridors for parkour-fighting Belgian private detectives should go without saying.
Great as a combat arena, impractical as anything else.
The mine has been abandoned since 1977, and since Hasard Cheratte is considered a protected heritage site, the very laws designed to keep it untouched make it ripe for hostile takeover. All that's keeping you from setting up evil shop is some barbed wire, a polite "keep away" sign, and an army of mustachioed, beret-wearing sentient gorillas.