Giant rings are necessary for getting through all the levels of Sonic Superstars. Not only do they give you medallions and extra rings, but they also supply all the Chaos Emerald powerups. You need to find at least one big ring in each act to unlock each of the emeralds.
Where to find all the big rings in Sonic Superstars
There are a grand total of 11 worlds in Sonic Superstars, and most acts have a few in each level. While there are most likely more than what is listed here, these are all the giant rings I have found in each level so far.
World 1: Bridge Island, Act 1
Find the first giant ring of Sonic Superstars right after the second set of checkpoints. The second big ring will be down closer to the bottom of the stage right before the boss.
World 1: Bridge Island, Act 2
Giant ring number one in this stage is close to the first checkpoint, floating above the palm trees. The second, as pictured below, is late in the level, fairly close to the bottom and the boss.
World 2: Speed Jungle, Act Sonic
In this Sonic-exclusive level, there is one giant ring that I have found; it is located to the right of the first set of rotating platforms. Once the sixteen rotating platforms spawn, jump all the way up them on the right side and take the path to this giant ring.
World 2: Speed Jungle, Act 2
In Speed Jungle's first level, there is one giant ring after the second branching speed tunnels; go through the bottom branching tunnel, then choose the middle branching tunnel from the second set. This will lead you right to the first big ring. The second big ring is about mid-way through the level, on the other side of the long, metal track.
The third giant ring is high up, to the left of the first spiral of vines that you can ride down. If you have Tails or the Emerald power that allows you to launch yourself into the air, this giant ring is fairly easy to get.
World 3: Sky Temple, Act 1
The giant ring in Act 3, level 1 is located as you fly up the big wind tunnel. There will be a bar on the way up, so be prepared to grab it do you can maneuver into this side tunnel. Another big ring is located immediately to the right of the column of golden balloons.
World 4: Pinball Carnival, Act 1
Both these floating rings are found in the middle of Pinball Carnival Act 1, at one end of the travel pipes.
World 4: Pinball Carnival, Act 2
There is an giant ring in World 4, Act 2 right after the second train platform. Take the first train, then jump over where the fire is. The second train will be hiding up there with some invisible platforms. The screenshot below was taken near the Tails' plush path; look for three spinning wheels that launch you. In the top one, there is a ring to the left.
World 5: Lagoon City, Act 2
Another giant ring hides in the underwater sections of Lagoon City. It will be right before the water tube that branches in three directions; head down at the juncture to get this one. The second can be found after the second suction tube, but just before the third. When you see little red fans in the water, swim up (this works best with Tails), and look for the hole in the ceiling to swim through.
World 6: Sand Sanctuary, Act 1
There is a giant ring right to the right of the countdown spinner.
World 7: Press Factory, Act 1
There is ring right before and right after the spinning spikes on the green screws.
World 8: Golden Capital, Act 1
This giant is located above the first golden blocks that grow up and left. Ride the ring cannons to the top, then use the floor panel to go into the back row.
World 8: Golden Capital, Act 2
After the long line of golden ring beetles that are unlocked by a golden watch, there is a giant ring floating at the end of that hallway.
World 9: Cyber Station, Act 1
In Act 1 of World 8, there is a big open area with three green slingshots along the bottom of it. There are some invisible platforms to help you reach the giant ring directly above the middle slingshot platform.
World 10: Frozen Base, Act 1
For more Sonic, check out Sonic Games Tier List – Best Sonic Games, Ranked on Pro Game Guides.