Hidden Island 15 is a lush tropical isle with fertile brown soil, grassy cliffs and palm trees. In the background, a view of the sea with small tropical islands and white clouds in the horizon can be seen.
Hidden Island 16 is different from every other Hidden Island in that it is much longer and larger than the others and has a multitude of alternate paths. It also borrows no exclusive gimmicks from other stages or focuses on a certain gameplay style. Instead, it has a more all-around layout and utilizes standard gimmicks, like Bungee Ropes, Winding Ropes, Dash Rings, Rainbow Rings, small platforms that collapse shortly after being stepped on, etc.
In the beginning, the player runs down a narrow platform to a Spring. From it, the player can either fall down to bottom and the lower path or reach a Grind Rail leading to two upper paths (where one of them lead to the lower path). Either way, the player eventually comes to a point where they can either take a simpler path through a passage above or take the longer route on the bottom. These paths will join together further ahead at a Winding Rope.
From there, the player can either reach an upper route with a Bungee Rope on the path or follow the bottom road, both of which will join together later. Following the Grind Rail after these roads unite, if playing as Blaze, the player can reach a faster upper path via a Spring and the Axel Tornado. Otherwise, the player only follow the longer ground route. These routes eventually join together on the stretch towards a Winding Rope. The player can then either ride the Winding Rope to a straight upper road or skip it to traverse a winding lower road, both of which lead to the Treasure Chest.