From Route 120, Route 121 proceeds east, passing a pair of Trainers (three Trainers in Emerald), two grass patches and a soft soil patch containing four varieties of Berries. The path passes through another grass patch before coming to a three-way intersection. The eastern path, blocked by a cut-able tree, is a shortcut that leads to the Safari Zone entrance. Trainers who lack the ability to use cut must head south from this intersection to a four-way intersection down two flights of stairs from the previous junction. To the west is a narrow, winding path leading to another Cut-able tree and a Secret Base location. South of here is the dock that leads to Route 122, which is a water route. Route 121, however, continues east.
After passing through another grass patch, Route 121 meets the shortcut path once again. From this point, Trainers can head northwest, ascending two flights of stairs, to arrive at the Safari Zone.
The main path continues east into a heavily fenced area. After entering another patch of grass, the route turns to the north and comes to another intersection populated by grass. The west path leads to a Trainer and an item, as well as a tiny patch of grass. The east path leads to another Trainer and another small grass patch. At the Trainer, however, the main path of the route turns south before curving to the east and passing through either a grass patch (Ruby/Sapphire) or the path of two Trainers (Emerald). East of the obstacle, a hole in the fence to the south leads to another soft soil patch with two Nanab Berry plants.
Route 121 curves to the northeast as it enters Lilycove.