Radiant Emerald is a course in Sonic R that is only unlockable after completing all other courses in Grand Prix mode. Doctor Robotnik is unlocked by completing a race here in first place (thus completing the game). There are no Chaos Emeralds on this course.
It is an extremely straightforward course full of long turns whose only shortcuts are unlocked via ring gates. This is the longest track in the game by far. Even after opening the short-cuts it still takes quite a while to complete a lap.
- There is a significant difference in this course in later versions - there is strangely a lack of transparencies in the PC ports whereas they were in the Saturn original. This is noteworthy since the true transparency effect was not believed to be possible on Sega Saturn since it was rare to see it happen on the hardware. In the PC ports, Radiant Emerald was instead made solid and textures made use of flashier lighting. This is also the case in Sonic Gems Collection.
- This is the only track in Sonic R that does not have weather. (Snow or Rain)
- This track is slightly similar to the course "Rainbow Road" from the Mario Kart series.
- This track has two songs. If the player is controlling Super Sonic, the song "Super Sonic Racing" will play. Otherwise, the song played will be "Diamond in the Sky."
- This is the only course that contains a dead-end.