I have an idea for a world to be a world tree.
The main part of the world would be a MASSIVE MASSIVE trunk that reaches endlessly into the sky. (if infinite height is possible… and if not… look at my 3d chunks idea on mine craft!!!!).
This trunk would be full of ‘caves’ dug out by insects and would have ores (mineral deposits absorbed by the tree and trapped in the growth rings of the tree. It would stretch for a grate distance… something in the lines of maybe 250,000~500,000 blocks or more. The bark would be thick and HARD to cut through and make good armors/tools, but once inside it’s a lot easier to hallow out.
The branches though twist and wind out almost endlessly, maybe to and wrapping around small planetoids.
MAYBE there could be a ground way way way way down there far from spawn…. but it would be full of massive and exstreamly deadly creatures. Though it could be a place to have a dungeon at the base in the roots that has some exstreamly grand rewards.