Pokémon FireRed and LeafGreen/Route 4

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.

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 for 500 Pokédollars. At first it is the weakest creature in the entire game, with pitiful stats and only two possible moves (one of which is useless). When it evolves, however, it becomes one of the most invaluable and fearsome colossi of all the Water-types: Gyarados. It's up to you whether you choose to by the Magikarp now or wait until you get an Old Rod to fish for one a bit later.

Items

 * TM05
 * Great Ball (hidden near the tutors, to the left)