Okay Mod Idea.

[CaveLag]

So, is it possibly to create a biome above grounds that are just like caves, but they are off to the side of the map, and the entrance, which would look like a sinkhole, to it would simply teleport you there. I thought of this because of the fact caves cause MAJOR lag because it counts as a separate server. I just would like it so people don't have to deal with lag.

[Bumber64]

I don't think this would help at all. You're just cramming all the same stuff into a single shard.

[Lokena]

I definitely saw such a mod existing. Without teleportation, though - the entire layout of caves, ruins and atrium is simply transferred to the main world, and you can swim to them on boat.