I remember issues where one of DC's house artists would occasionally draw up a diagram of what they think the Batcave would be like and I'm curious as to what my other chthonians here think. Here are some ideas I have about the 'Cave:
-- The Batcave is vast, probably several square miles in area, and it just happens to open up right under Wayne Manor. Old Papa Tom thought of everything.
-- It has several chambers with EXTREMELY high vaults.
-- The zillions of bats inhabiting have their "own" preserve, so they're probably not hanging over all the Bat-Gear raining down guano all over it. They can come through small corridors and tunnels from their preserve if swarming is needed. And they're a unique species of bat that aren't stinky.
-- There are large underground river channels in it for submarines, Bat-tleships, aircraft carriers, and yachts.
-- Alfred carefully tends several acres of pastureland within the "Cave and uses plant lights so that Bat-Cow will have a place to roost in between moon voyages.
-- There are openings within the Batcave large enough to drag giant pennies and T-Rexes through for trophy display within some of the vaulted areas.
-- Bruce owns the "mineral rights" to all ground above and below the 'Cave so that nobody can lay claim or start expeditions in it.
-- There is at least one area paved and walled in with level fire-proof stone suitable for use as a jet runway.
-- Alfred did all the construction work himself when he wasn't singlehandedly cleaning the Manor, cooking all the food, tending the jillion acres of manicured lawn and grounds, driving orphans around to school functions, and doing all the mechanical work on all the vehicles. He also uses a wheelbarrow to drag around all the Purina Bat-Chow.
-- There is no methane problem in the 'Cave, even when Bat-Cow eats bad grass or The Dragon burps.
Any more Batcave facts and fancies? I tossed out a bunch of silliness above, but such a cave would probably have been formed out of limestone. It must be gigantic. I don't recall any stories about amateur cave explorers stumbling into this thing, but maybe someone else has seen one. I've seen stalactites and stalagmites in it. There must be many huge chambers in it. How could Bruce keep something like this a secret--and I'm not talking about villains here. It's not in a remote location like the Fortress of Solitude, it's under the man's own house. The Manor probably stands on a few hundred acres, but such an immense cave could stretch on for miles. I don't recall Bruce ever saying whether he had even explored it all.