Route 9 is an east-west route located east of Cerulean City in northeast Kanto. It is one of the few routes in the Pokémon world that is not easily accessible at one of its termini. To reach Route 9 from Cerulean, trainers must either use Cut to remove a tree at the southern extent of the city to reach a pathway that links Route 5 to Route 9 or travel through a burglarized house to reach the same pathway. Either way, Route 9 is separated from Cerulean by a Cut-able tree at its western terminus. Its eastern terminus is at Route 10 north of the Power Plant.

The Rock Tunnel is a naturally formed underground tunnel. Because it has not been developed, it is pitch black inside. A light of some sort is needed for travelers to find their way. It is recommended that Pokémon Trainers bring along a Pokémon that can use Flash outside of battle.
Rock Tunnel is the only alternative route to Lavender Town, as any other route has either been rendered inaccessible by a slumbering Snorlax or the Saffron City gatekeepers. The cave has two separate floors, both of which are roughly the same size.
Route 10 leads from Cerulean City to Rock Tunnel. At the northern entrance of the cave is a convenient Pokémon Center. The roof of the Power Plant can also be seen from here (excluding Generation III). The southern entrance exits onto the remainder of Route 10, leading to Lavender Town.