Shadow arrives at Circus Park searching for the fourth Chaos Emerald. As he approaches the carnival, he spots Tails flying overhead in the Emerald-powered Cyclone. For an unknown reason, Tails crashes his plane (the fox is most likely shot down in the crossfire between Eggman's defenses and an attacking force of G.U.N. troops, bailing out and leaving the Cyclone to spiral away into the distance), and it is later revealed that he came to retrieve the rings that Dr. Eggman had stolen. Undaunted by his violent arrival, Tails suggests to Shadow that they should team up and recover all the rings Eggman has collected in the park. Further in the level, Shadow runs into the Egg Monitor, who conversely asks Shadow for his help in defeating the "G.U.N. geeks". The player can choose to help Tails recover the rings, eliminate the G.U.N. robots, or simply find the white Chaos Emerald.
Weapons
The following weapons can be found in Circus Park:
Following Checkpoint 2, the paths go to the left and right. To get the key you need to jump toward the hole in the center and use the Homing Attack to bounce off of the spring.
Right before Checkpoint 3, turn around and find the key in Eggman's box.
Grind the ropes with the four shooting gallery boards and then drop to the bottom with the two Beetles. The key is in the back.
Use the rocket after grinding down the long string of ropes. When you reach the other side, drop down to the bottom level, turn around and jump to the key.
Exit the circus tent and ride the roller coaster. You can get the key by holding left while riding it.
Defeat all 20 of the G.U.N. enemies in Circus Park.
Many of the G.U.N. Beetles are off the beaten path, so you may need to explore to find some. Four should have been defeated by the time you reach checkpoint #2, 10 by checkpoint #3, 13 by checkpoint #4, and 15 by checkpoint #5. The last five lie after checkpoint #5.
Although initially there are not actually 400 Rings in the level, there are special ways to earn bonus rings. These include:
Shooting Gallery - To begin, shoot one of the large disks that looks like a clock. Balloons will then rise around Shadow, which he must shoot to earn rings. There is also a green bonus gauge which fills as balloons are hit; filling it completely earns Shadow an extra 50 rings. Shooting purple balloons, however, causes the gauge to decrease and Shadow to lose rings.
Being launched into a nose that looks like Eggman - This becomes very helpful, when approaching one of these "noses" and later, the checkpoint after it. Use it to travel back to the checkpoint before the "nose", then replay it. Shadow will get 50 rings each time.
Flaming Hoops - Jumping through a fire hoop earns Shadow 5 rings.
What do you think of the world's greatest theme park? Like it?! 
