Void

The void (Japanese:  inside the walls) is the black area that surrounds indoor areas in the Pokémon games. All areas, indoors and outdoors, are surrounded by a tiled image, or in the case of Generation IV, an empty area. For most routes and cities, this tiled area is trees or water, or even rocky cliffs; however, as indoor areas tend to take up a small part of the screen, they must be filled with a blank tile to complete the illusion of being just a small part of a continuous world.

From Generations I to III, the void is completely inaccessible, and attempting to walk into it using a walk-through-walls code only results in the game crashing.

In Generation IV, the void is minimally programmed, as the player's location in Sinnoh's over world corresponds to the location they would enter in the Underground, and can be accessed through glitches, such as the Surf glitch and tweaking. Though the area between route and city areas remains covered in impassable trees, the void around an indoors area is, for the most part, clear to walking or running. Despite this, it can lock a player in, and the player can save here, leading to a potential need to restart the game from the beginning. However, accessing the void in can lead to a player being able to access Seabreak Path and Newmoon Island, and therefore the ability to capture  and, respectively, without the need for an official event item.

In Generation V, the void can be seen when riding the Rondez-View Ferris Wheel in Nimbasa City.

There is no known way of entering the void without hacking in Generation VI and Generation VII.