Team Rocket’s Hideout is a secret area beneath the Rocket Game Corner in Celadon City. Gain access by interacting with the rocket poster behind the guard.
The stairs will lead down to the first basement floor. South of the exit is a “beautiful spy.” Speak with her and say that you’re here to beat Team Rocket. She’ll give you the Team Rocket Set for you and your Partner Pokemon to wear.
Go northwest to fight the first member of Team Rocket on this floor.
To the west is a staircase down another floor, but you should avoid it for now. Further west are a series of weird tiles. Step on a blue arrow tile and you won’t stop until you hit a yellow stop tile. Two arrow tiles will be at the start. Step on the bottom tile to reach the northwest corner of this room. Walk around the barriers to the north to find a Nugget.
Return to the northwest corner of this room, then walk a few steps south to an Awakening in a corner. A short distance to the east is TM05 Rest, a status move that puts the user to sleep while fully restoring its health.
Step on a few of the arrows to reach the far southwest corner of the room. A PP Up can be found here. This item will increase the maximum amount of PP a move has. It’s useful on the powerful moves with few PP like Blizzard, Earthquake, or Hydro Pump.
Head to the far southeast corner of this room. A staircase will take you to another room with two more members of Team Rocket. There are also 5 Great Balls north of the staircase and a Hyper Potion in the back left corner.
With this room cleared you can return to the previous floor. Notice the elevator / lift near this staircase because you’ll need to return here later. For now, head to the north side of this floor and take the staircase down to the basement third floor. Another member of team rocket is guarding TM20 Dark Pulse to the south.
Defeat the Grunt to receive P812. Don’t forget to pick up the TM after the battle. Walk over to the northwest corner of this room next and pick up the Revive.
A series of tiles are positioned on this floor just like the last. Two tiles will be pointing left and right from the starting position. Take the arrow tile to the right first to pick up the Rare Candy.
Return to the starting point of this area, but this time take the arrow tile on the left. A few steps down is an X Speed.
Walk further south until you reach the final two tiles pointing to the right. Take the second-to-last tile to reach the southern portion of this floor. Follow the path around the corner and battle another Grunt.
Unfortunately the Grunt won’t hand over the key just because you beat him at a Pokemon battle. Investigate (press the A button) the air vent to the right of the white desk, then investigate the blue chair near the desk. This will allow you to send your Partner Pokemon into the vents.
You’ll now be controlling your partner Pokemon. Walk to the right and press the A Button to see a short scene with the Cubone. Walk to the left after the scene and exit out of the vents. Crawl along the pipes until you can pick up the Lift Key near Team Rocket.
Return to your Trainer and head back up to the elevator on B2F. Now that you have the elevator key, you can take it lift straight down to B4F. Alternatively, you can go to B1F to fight another Grunt of Team Rocket guarding the exit.
Take the elevator down to B4F when you’re ready to take on the heads of Team Rocket. Walk to the west first and pick up an Elixir in the corner. Jesse and James of Team Rocket will be guarding the door to the boss’s office, and will challenge you to a double battle.
Archer isn’t that tough of a boss since he only has two Pokemon, both of which are Poison-type. Use Psychic-type attacks to deal massive damage. Defeat Archer to receive P3,300. Heal your team before speaking with the man in the back, the boss of Team Rocket, Giovanni.
Giovanni is the leader of Team Rocket. He will use two of his favorite Pokemon, Persian and Rhyhorn. Persian is a normal-type Pokemon with normal-type attacks. Use fighting-type attacks to deal massive damage. As for the ground/rock-type Rhyhorn, this Pokemon is very slow and 4x weak to either water- or grass-type attacks. Hit hard and fast with those special attacks before he can land some strong physical hits.
Defeat Giovanni to receive P5,600. He will also hand over the Silph Scope, a special item that allows you to see all the ghosts in Lavender Town’s Pokemon Tower. That should be your next objective. Before leaving, investigate the small table in the back of the room to find a hidden Max Revive.
If you haven’t cleared Celadon City’s Gym and earned the Rainbow Badge, that should be your next objective before going back to Pokemon Tower! You can also speak to the man in front of the Rocket Game Corner to teach your Partner Pokemon a new secret technique: Sky Dash. This allows you to quickly fly to any previously visited town in Kanto.