It takes place on some kind of flying fortress in the clouds that consists mostly of rails, some riddled with spikes. It features things like Hang Gliders, parachutes, and rocket boards. It is also the first of two levels with non-bottomless pits (the second being Dead Line). These are actually big, horizontal laser beams at the bottom of some these pits that the player must avoid because touching them causes instant death as if the player fell into bottomless pit. There are also some 3D areas where the player flies around in a hang glider, collecting rings while dodging enemies; the player is not able to attack them. The song for Altitude Limit is "Get Edgy".
When playing as Sonic, Special Generators appear throughout this Zone which can warp the player to the sixth Special Stage for a chance to collect the cyan Chaos Emerald. As Blaze, the grey Sol Emerald can be found after defeating the boss.
The boss is the Egg Eagle. It is fought on a high metal platform on top of the clouds and tries to destroy the player by jumping on them or crushing them with its beak. It will even try to blow the player off of the platform by using its wings as a giant fan.