What makes a good party base of operations?

[TheCountAlucard]

Let's see...

Ancient metropolis built by our past incarnations, buried in the sands for over a thousand years, powered by a giant robot in desperate need of maintenance, and surrounded on all sides by roiling chaos (Exalted, we spruced up the place a bit, of course)
Hunting lodge sitting atop a cloud (3.5, though the PCs eventually ended up selling it)
Abandoned mining facility that dug too deep and unleashed unspeakable horrors (Exalted, after some necessary pest control was done)
The 24-hour fort (3.5, basically all the party casters devoted their higher-level spell slots to "Wall of Stone")
A massive black fortress-manse, constructed on the back of a miles-tall, half-dead behemoth enslaved to the will of its owner, staffed by armies of war-ghosts and Oblivion-maddened nephwracks (Also Exalted, though we never actually took it for ourselves... )
A handsome apartment complex, with high-end Matrix security set up by the party hacker/rigger, and literally more trideo channels than our street sam could count (Shadowrun, was a fairly nice place)