LSOV's Better Caves is a mod that aims to improve caves. It adds new biomes underground, new blocks, and a new dimension for players to explore and dig for resources in.

New Biomes:

Limestone Cave - The limestone cave is a cave that generates with new types of stones that can be used to increase a builders options of blocks.
Cobblestone Caverns - The cobblestone caverns is a biome made completely of cobblestone. It adds new colors and textures to otherwise boring looking caves.
False Surface - The false surface is a biome meant to mimic the look of the overworld by being made of grass and dirt, so don't be fooled when you try resurfacing.
Burning Caves - The burning caves are a dangerous biome made of molten obsidian that adds tough challenges for navigating gaves. Be sure to bring lots of fire resistance if you hope to survive here.
Simple Cave - This biome is exactly like a vanilla cave, so that you can still find vanilla biomes in the cavern realm.

Blocks & Items

Diamond Crystals - Diamond crystals are blocks that will naturally generate in caves. They can be mined to harvest 2 diamond shards. It will be shattered if hit by a projectile
Diamond Shards - Diamond shards are the equivalent of diamond nuggets. You can craft 9 of the together to make 1 diamond
Compacted Cobblestone - Compacted cobblestone can be crafted by combining 9 cobblestone blocks. This can be done to save inventory space or to go to the Cavern Realm.
Molten Obsidian - Molten obsidian is a dangerous block that will burn you to touch. It slows movement when walking on it. When broken, it will break apart into a current of lava. It can be obtain by smelting obsidian in a blast furnace.
Cave Root - Cave roots are rare plants that will only grow in bright areas in caves. They can be used to make a suspicious stew that gives haste.

The Cavern Realm: The Cavern Realm is a new dimension that is made entirely of caves. Here, you can mine for hours and gain large amounts of resources. It is also the best place to get oil.

To get to the Cavern Realm, you will need to build a frame out of compact cobblestone. This is the same type of frame the nether portal uses. Then, you will need to use molten obsidian, a blaze rod, and a diamond to craft a key using the recipe below.

How to craft the key

Once you have the key, you can light the portal and explore the Cavern Realm.