Radiant Emerald

Radiant Emerald is a course in Sonic R that is only unlockable after completing all other courses in Grand Prix mode. It is an extremely straitforward 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.

Doctor Eggman is unlocked by completing a race here in first place (thus completing the game). There are no Chaos Emeralds on this course.

The theme song for this course is usually "Diamond in the Sky", although when playing as Super Sonic the song played is instead "Super Sonic Racing".