Minecraft wiki entry for World_boundary, associated text: Traveling from one edge of the world to the opposite edge by powered rail would take 35 days and 10 hours. Building the rails for such a trip would require enough iron and/or gold to fill over 723 double chests, even when packed into blocks, as well as sticks made from enough wood to fill over 135 double chests (as log blocks, not as planks, and excluding the redstone torches). (53 stacks of logs would be required just to make enough chests to hold all the building materials for this rail track.) If already crafted, the rails required would fill 17,361 double chests. If the player had to gather the materials to make all those rails, they would wear out 14,404 diamond pickaxes and 300 diamond axes (on average, about 3,601 diamond pickaxes and 75 diamond axes, both enchanted with Unbreaking 3).
Even if one were to amass all these materials, actually laying said track would require the player to travel the entire distance through other means anyway.
Factoring in the need for powering the track and assuming the player were to use redstone torches, the player would require 3,529,412 torches for the full track, since a torch can optimally light 17 blocks. That requires 55,148 sticks and bits of redstone dust, which requires 2042 large chests, which requires 128 stacks of log blocks to make the chests (which requires 3 large chests).
Traveling from 0,0 to the edge of the world by foot takes around 140 days.[7]
From -29999984, 0, -29999984 to 29999984, 255, 29999984 there is a total of 921,599,016,960,262,144 (921 Quadrillion) blocks in the default world border (Including air blocks)
It is possible to generate trees and vegetation beyond 30,000,000 by loading a version of Minecraft after Java Edition 1.9, then load a few chunks beyond the world border. Then, close the world and load a version of Minecraft between Beta 1.8 - Release Java Edition 1.6-pre[verify] and load the same world. If the players travel to the world barrier, there are a few chunks that generate beyond 30,000,000 that have trees and grass.
It is possible to even generate Far Lands chunks using this method. Load a world in release Beta 1.8 - Release 1.6 and teleport to X/Z: 30,000,000. Close the world before the fake chunks generate and load the world in Beta 1.7.3. The Far Lands chunks load and then, the player can load as many chunks as they want. Then close the world and load it in a newer version, and the player has Far Lands chunks in the 30,000,000 block area.
Spiders can climb the border, continuing to climb upward indefinitely.[verify].
In Minecraft 4k, there is a barrier on the bottom of the map, which is unbreakable by any means.[8]