Diamond Dust Zone

Diamond Dust Zone is the fourth zone of Sonic 3D for the Sega Mega Drive and Sega Saturn, coming after Spring Stadium and before Volcano Valley Zone.

Description
As with other stages in this game, Diamond Dust consists of two standard Acts followed by a third Act containing only the boss fight. In Acts 1 and 2, Sonic must free captured Flickies from inside badniks, depositing five of the birds into a Goal Ring to progress between sections of the level (usually three per Act). This Zone is filled with snow blowers that can freeze Sonic, which doesn't damage him, but forces him to jump a few times to break himself free. There are also rivers of slush that Sonic can walk one, but lead to frozen spikes, as well as frozen crystal that he can break by spinning, but still hurt him if he touches them. Geographically, the Zone is located on Flickies' Island, presumably on the outer slopes of its volcano, considering the next stage.

Boss
In keeping with the icy theme, Robotnik has augmented his Egg-O-Matic with eight freezing-gas pods he has dotted around the level. Eggman begins as usual, hovering tantalizingly above Sonic's reach, but he'll soon swoop down and attempt to blast the hedgehog with a jet of cryogenic vapor. The nozzles fire cyclically, so the player must land a hit on Eggman when the wave of chilling gas is on the other side of his vehicle. To spice things up a bit, Eggman occasionally drops exploding snowmen onto the battlefield.

Trivia

 * A remix of the background music from the Mega Drive and Sega Saturn version of Diamond Dust Zone Act 1 is used in Sonic Chronicles: The Dark Brotherhood for Central City and Blue Ridge Zone respectively.
 * The Diamond Dust Zone Act 1 music from the Sega Genesis version of Sonic 3D Blast, is present as an unlockable track in Sonic Generations. To unlock it, all challenges must be cleared.