Why can't I find caves?

I'm pretty sure I covered all of my map with my friend but I still can't manage to find caves.

How is that ?


Solution 1:

After wondering for about a day, we finally found out that there's an option that is not enabled by default in the world creation.

Add Caves option on the World tab in the World Creation menu.

This option is disabled by default because it requires the host to have 2 worlds (top ground and caves) running at once, which drains a lot of resources.