Special Stage (Sonic the Hedgehog 16-bit)
From Sonic Retro
In Sonic 1, if you complete Acts one or two with fifty rings or more, a gigantic ring will appear above the signpost. Jump into it and you'll be transported to a rotating special stage where your goal is to find, and touch a Chaos Emerald.
Failing that, you'll get a bonus to your score, and even an extra life or two.
