How could I have massive subterannean space on my world?

I would like a world with a big LOT of subterranean space to explore, colonize, and trap ancient evil beings.

Now, while the questions about food and ventilation are well adressed on Worldbuilding, I would like to ask the question geologically speaking.

From what I understand, caves on Earth can be :

• Limestone cave
• Lava Cave
• Artificial caves (quarry...)

The first one exists with system up to 200 km large. The second seems more anecdotic. The tird one doesn't concern us.

What I'm asking for :

What types of cave could we encounter in a World like this, what conditions would create them, and what geologic impossibilities could I encounter ?

What I thought of :

More limestone, More ancient world, allowing more time for nature to carve these caves, More Volcanic activity, More Rain

How can a world with somewhat similar surface to the Earth's one develop these very large underground formations ?

Edited : I did send a sketch at first, sorry.

posted over 6 years ago

GlorfSf‭

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