From Bulbapedia, the community-driven Pokémon encyclopedia.
Cerulean Cave, known as the Unknown Dungeon in Generation I, is a cave located northwest of Cerulean City in Kanto. The cave is home to 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. The cave has existed in every Generation with the exception of Generation II, when the cave was sealed off.
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 bringing the Network Machine to operate.
Items
Generation I
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
Pokémon Yellow
- 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
Generation III
- 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
Pokémon
Generation I
American
Japanese
Pokémon Yellow
Pokémon FireRed/LeafGreen
Differences among Generations
The layout of the cave has been tweaked several times, particularly in Generation I.