After traveling throughout the Kanto region and defeating the eight Gym Leaders, the end of the story is fast approaching. The last great challenge for aspiring Trainers is to defeat the Elite Four far to the northwest, at Indigo Plateau. But before reaching the summit, you must travel through Victory Road, a grueling cave that serves to weed out the weaker Trainers. Rest your team and stock up on items while you can; the third legendary bird roosts deep inside the cave, so plan accordingly.
As you travel west on Route 22, Blue shows up to challenge you one last time. His Pokémon are no pushovers, but play to their weaknesses and they won't last very long.
Route 23 is a long route, and Victory Road awaits at the northern end. Be sure to have access to Surf, or you won't get very far.
The guard in the front gate checks all Trainers for the Boulder Badge. Scattered to the north are seven more guards, who each check for one of the other seven badges. Once the eighth guard sees your Earth Badge, you are free to enter the cave.
Inside the entrance is a boulder to the west and a switch to the east. To activate the switch, move the boulder ↓1, →4, ↑2, →7, ↑2, →1, and ↓1. This removes the semi-invisible barrier on the rock platform. Head up to the northeast area to find two items near the north wall. The cave's layout forces you to use the boulder here to block off one item in order to reach the other. A Rare Candy lies to the west, while TM43 (Sky Attack) lies to the north. In order to reach the other item, exit and re-enter the cave to reset the puzzle. Go west past the two Cooltrainers and climb up the ladder in the northwest.
Victory Road, 2F
To the south is another boulder, move this one ←1, ↓2, ←2 onto the switch to clear the rock platform. Walk across the ledge, and go down the first stairway. To the west is TM05 (Mega Kick) and a pressure switch. Head northeast to find a Full Heal and TM17 (Submission), and climb the ladder near the Full Heal to the third floor.
Victory Road, 3F
To the north is another boulder, but ignore it for now. Go east to fight a Cooltrainer♂ and get a Max Revive. Head to the northwest area to find TM47 (Explosion) and another switch. Climb down the ladder to reach a new part of the second floor.
Moltres, the legendary bird of fire
Fight the PokéManiac and grab the Guard Spec., then save the game. Roosting nearby is Moltres, the third and final legendary bird. Follow the same methods used against Articuno and Zapdos to complete the trio, then climb back up the ladder to 3F.
Go back east to the first boulder and move it ↑2, ←16, ↓1, ←4, ↓3, →1 to reach the switch. This clears the barrier on the rock platform so you can reach the southern area. Walk across the platform and head south to battle two more Cooltrainers. Go east to drop the boulder down the hole, then jump down behind it.
Shove the boulder all the way west to the switch. This removes the barrier near where it fell through from 3F. Climb up onto the platform and take the ladder back to the third floor.
Climb down the next ladder back to 2F.
Check the rock west of the ladder to find a hidden Full Restore, and leave the cave to return to Route 23.
Follow the tiled path to the north, and wander through the maze of Pokémon statues at the foot of the Indigo Plateau. This is it!