The Rock Tunnel Connects Route 10 to Lavender Town. To get through, you need to have a Pokémon that knows HM05 - Flash.
If you picked Squirtle or Bulbasaur as your starter and leveled it up decently, you'll have little problem getting through. Those who picked Charmander as their starter will struggle though, as the Rock types here are super effective against Fire types. Pick up as many Super Potions as you can in Vermillion City, as you'll be using them. For now, worry about getting to the other side and come back for the items/Pokemon later once you have a stronger team.
On the second level, in the southwest corner, there is a Move Tutor who will teach your Pokémon Rock Slide.
|FireRed||Level||Encounter Rate||LeafGreen||Level||Encounter Rate|
|#66 Machop||#95 Onix|
Although not as well rounded as a fully evolved Golem, Onix's Defense stat is unmatched. In addition, he receives Dragon Breath at level 30 and Iron Tail, at level 45, making him a contender for use against Lance's Dragons in the Elite Four.
However, be sure to remember that Onix's Rock/Ground types make it extremely weak against Water and Grass Pokemon. Onix will evolve into Steelix when traded holding a Metal Coat. This cannot happen until beating the Elite Four however.
Trainers in Cave
|1||Ashton||Cubone 23||Slowpoke 23||1104|
|3||Martha||Oddish 22||Bulbasaur 22||440|
|4||Steve||Charmander 22||Cubone 22||1056|
|6||Eric||Machop 20||Onix 20||720|
|7||Lenny||Geodude 19||Machop 19||Geodude 19||Geodude 19||684|
|8||Oliver||Onix 20||Onix 20||Geodude 20||720|
|9||Lucas||Geodude 21||Graveler 21||756|
|10||Sofia||Jigglypuff 21||Meowth 21||Pidgey 21||420|
|11||Dudley||Geodude 21||Geodude 21||Graveler 21||756|
|12||Cooper||Slowpoke 20||Slowpoke 20||Slowpoke 20||960|
|13||Leah||Bellsprout 22||Clefairy 22||440|
|14||Ariana||Pidgey 19||Rattata 19||Rattata 19||Bellsprout 19||380|
|15||Dana||Meowth 20||Oddish 20||Pidgey 20||400|
Trainers outside Cave
|16||Carol||Pidgey 21||Pidgeotto 21||420|
|17||Clark||Geodude 21||Onix 21||756|
|18||Trent||Onix 19||Graveler 19||684|
|19||Herman||Cubone 20||Slowpoke 20||960|
- Max Ether (North of Picnicker Sofia and Hiker Dudley)
- Revive (B1F; southwest corner)
- Escape Rope (Southeast of Hiker Lucas)
- Pearl (North of Picnicker Dana)
- Repel (1F; northeast corner)