How to create a huge cave of 2 Km x 2Km?

Development World Creation
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1

Hi,
We need to make a huge cave (inside a mountain). I have no idea what is the best way to make this.
For caves, normally meshes are used. But this cave needs to be about 2Km x 2Km! And close to the walls it should still look good. So no triangles of 1 x 1 meter or so.
What would be the best way to create such a huge cave? Please give us some ideas.

2

Maybe, use 2 landscapes - one for floor, and one for ceiling? Or more, if your cave must have layers.

3

I didn’t know that was possible. Would be great. So I can add two extra landscapes below the main landscape? And set one as a ceiling?

4

You can have more than one landscape. I don’t see a reason why they can’t be placed one on top of other.