subterrain 0.2.0 by paramat
For Minetest 0.4.12 and later
Depends default
Licenses: code WTFPL

A fast, very simple mod to develop and replace the big caves of the now removed 'indev' mapgen.
By default massive caverns start to appear below y = -256.
Realm limits, blend distance and cave size / underground volume ratio are parameters for you to adjust.
By default caves are roughly 1/3rd of underground volume, and can be separated by up to roughly 800 nodes.