Kanto Route 11
From Bulbapedia, the community-driven Pokémon encyclopedia.
Route 11 lies directly east of Vermilion City. There are many grassy areas, and several enemy trainers. There's an entrance to Diglette's Cave on the west end of the route. The other end opens up on the east side of Route 2.
The west end of Route 11 ends in a lookout station that connects it to Route 12. However, a sleeping Snorlax may block the way, and to move it, a Poké Flute or a PokéGear playing the Pokémon March may be required.
In the lookout station is one of Professor Oak's aides. In the Generation I games, he'll give the main character an Item Finder if their PokéDex has 30 different Pokémon registered.
