Instructions
Obtain all eight badges in the Kanto region. Walk west from Viridian City and cross over into Route 22. Keep going west into you reach the Pokemon League's Front Gate, which takes you into Route 23. Eight guards will check for your eight badges. Pass through to get to the cave called Victory Road.
Enter the cave and look for the boulder by the entrance. Use the "Strength" ability to push the boulder far to the right. Rest the rock on the white circular switch. Walk back to the left where you found the boulder and walk up the stairs.
Walk up until you see the purple-haired trainer. Turn left and go down the stairs. Turn left again, walk up and ascend the rope ladder beside the second trainer. Walk through the path until you see another boulder and another switch. Use "Strength" to push the rock onto the switch. Turn around and walk up the stairs and turn right.
Head south when you run into the trainer with the white headband. Go down the stairs beneath the trainer, turn right and walk until you reach the dead end. Walk up and to the left. Ascend the ladder beside the brown-haired trainer walking in a circle. Look directly up on the map for another boulder. Use "Strength" to push the boulder up and to the left. Rest the rock on the switch.
Walk back to the right. Go up the stairs where the purple-haired trainer is standing. Head down through the path until you reach another flight of stairs. Walk down and head right, past the two purple-haired trainers. Push the boulder into the black hole, and jump in after it.
Use the "Strength" ability to push the rock on the switch to the left. Go back to the right, head up the stairs and go up the ladder. Walk past the two trainers standing side-by-side and go down the next ladder. Run to the right and head through the door to exit Victory Road.