Different biomes, different caves.

To incentivize exploration(even further), i thought that it would be interesting if different biomes would have different caves underneath, and those caves would have their own biomes, so essentially each surface biome would have it's own specific set of underground cave biomes with unique game mechanics, challenges, items/loot and mobs that you can only get and see in them, this will make players want to go to different places to gather their unique resources.

For example: If you go to a icy biome you will find ice themed caves underneath and it could have puzzles and challenges around sliding on icy floor. Underneath the desert biome you could have caves with quicksand that you need to be smart and creative to maneuver around.