Instructions
Travel through Route 10 from Lavender Town and enter the Rock Tunnel's entrance near the end of Route 10. Use the Flash move to light your way through the tunnel while heading left to go down the ladder ahead.
Use the Rock Climb move to get the items Oval Stone, HP Up and Iron, which are located above several walls on Floor B1. Walk around the rocks surrounding both middle walls and head up the nearby stairs to the first floor.
Head right and then up upon reaching the first floor again. Go left to reach two sets of stairs leading toward a cliff; follow the top path along the wall to reach another ladder.
Head down the ladder from the first floor to reach Floor B1 again. Walk forward to find two paths; the upper path leads to a small room containing the item Revive, while the bottom path leads to the next two routes ahead. Head right to reach the last two routes. Take the left path to reach a ladder leading to the exit of the Rock Tunnel.