Route 4 is a short path in north Kanto from the eastern exit of Mt. Moon in the west to Cerulean City in the east. Though the official western terminus of Route 4 is at Route 3 south of Mt. Moon's western entrance, the western terminus is regarded by most to be Mt. Moon's eastern entrance.
The first Pokémon that is exclusive to Pokémon FireRed. It's hard to train him, but it can become quite useful later on in the game after you evolve him.
The first Pokémon that is exclusive to Pokémon LeafGreen. It is also the first Ground-type Pokémon in the game. Easy to train and has powerful attacks that also include poison, bug and rock type moves, making Sandshrew very useful.
Route description
From Mt.Moon, Route 4 travels to the east, swerving to the north and the south to avoid ledges along the route. The path turns north, then east near a large clump of trees surrounding a grassy area. To the east of this area is a ledge that separates Mt. Moon from Cerulean. By hopping down this ledge, the trainer cannot return to the previous towns until they travel through Diglett's Cave and use HM01 (Cut) on Route 2, or use Hm02 (Fly) to return to the cities.
The majority of the route is fairly straightforward as there is only one true way to proceed on the path and there are no trainers to battle (with the exception of a Lass on the highest hill on the route; however, she is reached only by way of the waterway that begins on Route 24).
Pokémon Purchase
In the Pokémon Center in the beginning of this route there is a fisherman that will sell you a very special Pokémon.