Kingdom Valley

Kingdom Valley is one of the levels in Sonic the Hedgehog. It is north-east of Soleanna and once housed its old kings. In the game, Kingdom Valley is the site of one of Doctor Eggman's bases. Kingdom Valley is abound with water so the ancient ruins and weak wood platforms aren't the best footholds.

Sonic
In Sonic's story, he and Silver are in pursuit of the Egg Carrier before it explodes, killing both Eggman and Princess Elise. The first part is sonic running through ruins and trying to reach the Egg Carrier. The second part is Silver helping Sonic to reach Elise. It utilizes a High-Speed area at the end which takes place in a set of ruins encircled by rushing water that Sonic also needs to run along. This is the fourth and final high-speed area, after Wave Ocean, Crisis City and Radical Train.

Shadow
In Shadow's story, he and Rouge go to Kingdom Valley because it is the G.U.N rendezvous point for the Scepter of Darkness, which Rouge obtained in White Acropolis. Shadow must use a glider to pass through some of the level and a Hovercraft to cover a large water body. Shadow is ambushed by Dr. Eggman at the extraction point, which leads to Mephiles being released and taking Shadow's form. Mephiles then sent Shadow into the future to Crisis City. Shadow later returns here to find the red Emerald in the End of the World.

Silver
In Silver's story, he, Sonic, and Blaze chase after the Egg Carrier to rescue Princess Elise from the soon to be destroyed Carrier. Sonic then travels to the past again to successfully save Elise and gives Silver and Blaze his Chaos Emerald to return to the future.

Silver's act is considered the hardest. However, this can be argued by Sonic's high-speed area, as it requires careful jumping and timing.