From Bulbapedia, the community-driven Pokémon encyclopedia.
Cerulean Cave (Japanese: ハナダのどうくつ Hanada Cave), known as the Unknown Dungeon (Japanese: ななしのどうくつ Nameless Cave) in Generation I, is a cave located northwest of Cerulean City in Kanto. The cave is home to a wide variety of high-level wild Pokémon. Only trainers who compete and win in the Pokémon League at Indigo Plateau may enter due to the potency of the Pokémon in the cave. At the end of the cave lies Mewtwo, the only one of its species in the game.
Cerulean Cave has had many different layouts over time, getting a change from not only one Generation to the next, but also from one game release to the next. In Pokémon FireRed and LeafGreen, the layout is true to that of the original Red and Green games, aside from the addition of Rock Smash boulders.
Another addition in FireRed/LeafGreen lies in the fact that trainers are now required to further prove themselves before entering the cave, which is done by completing the quest on Sevii Islands and restoring the Network Machine to operational status. Another change is in the fact that more Pokémon can be found only by fishing, while wild Pokémon found just by walking around in the cave are reduced in number. In Generation I, there are also several species that make no sense to be in the cave, such as Dodrio and Pokémon that are otherwise only obtainable by stone-induced evolution, however, this has been fixed in Generation III, at the cost of some of the wild Pokémon diversity.
In Generation II the Unknown Dungeon completely collapsed. However, the leftovers of Mewtwo's presence can still be found in the lake near the cave, in the form of Berserk Gene.
Pokémon Red and Blue
- Full Restore: on the riverbank near the southwest corner of the first floor; center of the second floor
- Max Elixir: on the riverbank on the first floor
- Max Revive: north edge of the basement
- Nugget: near the northwest corner of the first floor
- PP Up: east edge of the second floor
- Ultra Ball: southwest corner of the second floor; center of the basement
- Full Restore: east edge of the second floor
- Max Elixir: west of the entrance on the first floor; north edge of the basement
- Max Revive: east edge of the first floor; southeast of the second floor's center; center of an elevated area in the basement
- Rare Candy: southeast corner of the first floor; west edge of the second floor
- Ultra Ball: center of the first floor; center of the second floor; center of an elevated area in the basement; northeast corner of the basement
- Full Restore: on the riverbank near the southwest corner of the first floor; against the eastern edge of the second floor
- Max Elixir: near the center of the first floor
- Max Revive: in the northeast corner of the basement
- Nugget: in the northwest corner of the first floor
- PP Up: near the southwest corner of the second floor
- Ultra Ball: near the southeast corner of the second floor; near the center of the basement
*=Indicates catch rate varies by floor. Rates are listed for Floor 1, followed by the Basement in that order.
Differences among Generations
The layout of the cave has been tweaked several times, particularly in Generation I.