It's possible you're thinking of:
* The Ilex Forest: This is a route in Pokemon SoulSilver located in the Johto region, where you encounter the legendary Pokemon, Entei.
* The Yellow Forest (from Pokemon Yellow): This is a route in Pokemon Yellow where you encounter the legendary Pokemon, Zapdos. However, it is not present in Pokemon SoulSilver.
If you're looking for specific routes or Pokemon in Pokemon SoulSilver, it's best to consult a guide or online resources for accurate information.