Forge World Secret
If you go on Forge World. You will start in a meal open cave, but there is somewhere cool that you can go. Directly north, there is a large island. If you started a new map of forge world, go into edit mode. Fly to the far side of the island. When you land. If you are still looking north, turn east 90*, you might see a small river of pooling water. Run through it, if you don't fall to your death, you should see a tunnel opening. go through it and you will end up at a gigantic land mass with many caves. This is way bigger than all the other islands combined.
Please do not comment badly on this cheat, even if you have already been there, just try it yourself. :)