Don't let the lush scenery, grassy platforms and cascading waterfalls fool you. Forest Falls is brimming with danger, including steep drop offs, large loops and plenty of Eggman's robot minions.
— Sonic Rivals Instruction Manual
Forest Falls Zone is the first Zone in Sonic Rivals and is located on Onyx Island, a future version of Angel Island brought to the present by Eggman Nega. A typical forest area in the Sonic series, the Forest Falls Zone serves as the starting point for all of the game's playable characters.
Overall, Forest Falls Zone shares many similarities with Green Hill on South Island, such as forests with a similar terrain. It is set in a temperate climate, with colorful and fresh green grass and flowers everywhere. This forest contains many waterfalls and rivers that flow through it. These waterfalls can lead into underground caverns within the purple rockfaces, where giant spiderwebs can be found.
When racing through this area, the player can take to the air, riding the winds on giant leaves, while the ponds found below have extremely large water lilies that can be used to hop across the pond.
Sonic and Knuckles
Having just arrived at the island,Sonic finds Eggman Nega, whom he believes to be Dr. Eggman, and ask what he has done to Tails and Amy. Then Knuckles arrives at the scene. He has been searching for the Master Emerald which had been stolen and his search had brought him to (the somehow familiar) Onyx Island. He accuses "Dr. Eggman" of stealing the Master Emerald. The "Doctor" explains to them that he used his special camera to turn Sonic's friends and the Master Emerald into cards. He then says that if Sonic and Knuckles want them back, they would have to catch him first, and the two rivals races after him.
Shadow and Silver
Six hours earlier, Shadow received a call from Dr. Eggman, who asks him to follow the transmission's signal. Shadow does so and ends up in Forest Falls Zone on Onyx Island. Shadow then spots Silver, who appears to be pursuing "Dr. Eggman", who really is Eggman Nega. Silver is merely after Dr. Eggman to question him about Eggman Nega. Unaware of this, Shadow sets off to stop him.
- Early concept artwork gives the name "Waterfall Forest", but was apparently changed in the final version of the game.