Hole
A hole is a special tile in various games that allows the player to fall into another floor of a building, or sometimes even caves.
Kanto Region
Generation 1
In Pokemon Red, Blue, Yelllow, and Green, holes are found in various locations. Perhaps the easiest to find is in the Seafoam Islands, where you have to push boulders down holes, and then follow them by going down the hole yourself. This would eventually lead the player to Articuno.
Generation 3
In Pokemon Firered and Leafgreen, holes are in the same location as in earlier Kanto Region games. However, in these versions, a special kind of hole exists in the Sevii Islands. In one of the islands, you are required to push boulders into these holes, which open up the path to the Tanoby Ruins.
Johto Region
Generation 2
In Pokemon Gold, Silver, and Crystal, there are holes that exist in Icefalll Cave. It is required to push boulders down these holes, which allows the player to go through different floors, where the player must push a Kimono Girl out of the cave, before the player can do so hemselves.
Generation 4
In Pokemon Heartgold and Soulsilver, holes exist in the Icefall Cave, and the point is the same as Pokemon Gold, Silver, and Crystal.
Hoenn Region
Generation 3
Sinnoh Region
Generation 4
In the games Pokemon Diamond, Pearl, and Platinum, there are holes in Snowpoint Temple, where the player must go through the five different floors, which will eventually lead the player to Regigigas, so long as the player has Regice, Regirock, and Registeel in their party.