You really need to post this on Fanfiction.net.
Well, according to one entry on tvtropes:
…Along with a couple of other explanations/versions of continuity regarding the subject.
I thought the cave was simply a natural formation.
Keep in mind that the contents of the cave are the accretion of over a decade of inhabitance (in current continuity), Bruce, Alfred, and Harold (and Dick, Jason, and Tim) adding to it as time goes on, and they need new toys, upgrades to old toys, or more room to store the new stuff, the old stuff they’ve replaced, and their trophies.
Well, presumably the basis of the cave is natural, or else he could have just built a bunker. But as Tom Tildrum notes, you can’t just run a couple of extension cords down and sweep the fresher guano into a corner if you want to make it a respectable command center.
Batman doesn’t like to talk about it but he ended up having to contract the entire job out to Stark Enterprises.
Compromise. He obviously uses Superman robots.
I prefer Professor Xavier’s method. Hire a regular construction company and just use your telepathic powers to keep them blind to weird happenings and mindwpe them afterwards. Perhaps J’onn does this for him.
Funny thing is, that’s how Northern Ireland’s armoured police stations were built during The Troubles. Amongst other things, such as how fast you can drive an APC past an old woman on the motorway, Dad learned that from a mix of ex police and military officers he works with.
They would chopper over workers from England, have them live and work in the stations under construction, then chopper them back when they were finished. For buying supplies within the province itself, police officers would create a front for themselves, some sort of small contracting unit, and buy up the supplies they needed.
Handy when workers could be summarily executed for doing nothing more than baking a nice loaf of bread.
Keep in mind that the contents of the cave are the accretion of over a decade of inhabitance (in current continuity)
What about the accretion from the regular inhabitants of this bat cave?
Villain Source makes no mention of building for the Good Side.
I’d wondered what had happened to that website. It used to go under a different name (villainsupply.com or some such) and I thought it was a shame when it shut down. I opened this thread specifically to mention it. I’m glad to see it back up and running.

Does that mean I shouldn’t mention that Alfred has superpowers that rival Superman’s, but he’s too much the consummate butler to draw attention to himself, or embarrass his employer?
When the Batbots arrive to wipe all our minds, I’m not saving any of your asses. I mean it. I’m just gonna world-hop over to Earth-616 where it’s safe.

I prefer Professor Xavier’s method. Hire a regular construction company and just use your telepathic powers to keep them blind to weird happenings and mindwpe them afterwards. Perhaps J’onn does this for him.
So…mindrape. Yeah, I can see Batman doing that, given that his moral modus operandi seems to be that there’s one set of rules for him and another set for everybody else.