I don't what it has been lately, maybe exploring tunnels on that beta server, or my 1.15.2 world but I want to play a mod that adds alot to the underground, like cool biomes, new structures or improved ones that already exist, preferably an old mod (pre 1.17), you can call the new giant holes that just spawn monsters an upgrade to intricate tunnel, ravine, and structure systems, whatever, I just want a cool underground mod. I also want the installation to be simple, but if the mod is very good I'll find a way.
Any cool minecraft cave mods?