The route is separated into two halves by a long ledge, placing the northern half on a hill. The northern half can be accessed by using Cut to remove a tree at its eastern entrance on Route 14. Trainers can travel from the northern half to the southern half at any time by hopping the ledge; however, the reverse is not possible.
Only two items of interest are present on the hill: Trainers and an item. In Generation III, the number of Trainers was raised from one in Generation I and Generation II to four. The change is sensible considering that by using the northern half of the route, Trainers can avoid a collection of no less than eight Trainers (six Trainers in Generation II) on the southern half.
In Generation I, the Trainer is located in the center of the hill and the item ball contains TM20 (Rage). Generation II removed the Trainer from the hill and replaced TM20 (Rage) with PP Up. Finally, in Generation III, the Trainers were spread out evenly over the western two-thirds of the route and the item of choice was TM18 (Rain Dance).
The hill comes to an end just east of the gate, where Trainers are forced to hop down to the southern half.
The south half of Route 15 runs directly east-west between Route 14 and Fuchsia.
From the eastern terminus, the main path of the route passes the first of four grass patches that lines the ledge that separates the route. The first two Trainers on the route (only the first in Generation II) are located here.
After a brief break in the grass, another patch begins near the next two Trainers on the route. Five paces to the west, the second patch ends and the route encounters its largest area without grass. Two more Trainers, as well as the Route 15 signpost, are found in this section.
Ten paces to the west, the third patch begins, followed by another brief break near another Trainer and, finally, by the fourth and final grassy patch near the last Trainer on the route.
The gate is located roughly four steps west of the final grass area. In the station, an aide of Professor Oak will give the main character an item if he or she has registered at least 50 Pokémon in his or her Pokédex. In Generation I, this item is an Exp. All. In Generation III, the item is an Exp. Share. There is no such reward in Generation II. Looking through the left binoculars will allow the player to see Articuno flying in the sky.
On the other side of the station, Route 15 continues for several paces before officially entering Fuchsia.
Only minor cosmetic changes exist between these generations. The fences in the north of the route are changed to trees in Generation III, trees are also added in the south of the route. Also, the road curves north and then west to the gate, unlike Generation I.
The number of grassy patches in Generation II were reduced from four to three, as well the length of the route was reduced by a third. The ledge that divides the route in two sections now turns to the north at the left end. This makes the south road curve to the north. Also, there is no path west of the gate.
Like most routes in Kanto, the main layout and size of the route is similar to that of Generations I and III, but with several changes. New ledges and trees are added to the route. The ledges can only be traveled from east to west in the north section, and west to east in the south section. This effectively makes the route similar to a dual carriageway.
The number of grassy patches in the middle is now two, however, the east patch now occupies nearly triple the space. The flowers of the center of the route are moved to either the north or the south of the paths. A new patch of tall grass is added in the northeast of the route. Also, like in Generation II, the ledge at the west turns to the north and there is no path west of the gate.