The CubeWorld mod for 1.7.4 breaks up your world into glass cubes. Each cube has a separate biome inside, complete with mobs and dungeons. If you travel to the Nether you will also find that the area is broken up into cubes, and even glowstone is in its own cube.
Download the CubeWorld Mod for 1.7.4:
CubeWorld Mod for 1.7.4
Go to %appdata%/.minecraft/versions.
You should see a folder named 1.7.2. Make a copy of it, and rename the copy to Cube_World_1.7.2.
Inside the new folder, you should see a file called 1.7.2.jar. Rename it to Cube_World_1.7.2.jar.
Inside the new folder, you should also see a file called...
The CaveGen mod adds a new Cave Type world to the game. This world is one giant cave. It’s hard to survive in the cave because mobs spawn everywhere, the lack of resources, and the lack of natural light. This world is especially hard to survive in with hardcore mode.