Gaia Gate

The Gaia Gate (ガイアゲート Gaiagēto?) is a type of portal that appears in Sonic Unleashed. They are ancient devices created ages ago that, once activated, act as instant transporters to different areas on their chosen continent, and are, apparently, powered by Light Gaia. There exist multiple Gaia Gates on Sonic's world, one specific set for each continent. In gameplay, the Gaia Gates serve as entrances to the game's different Action Stages and Boss Stages. Their layout differs greatly between the PS3/Xbox 360 version and the PS2/Wii version.

PS3/Xbox 360
On the PS3/Xbox 360 version, the Gaia Gates can be found inside the different continents' Entrance Stages. On these versions, the Gaia Gates are circular teleportation pads that are surrounded by a glowing cylinder of light and are scattered all over the Entrance Stage. These Gaia Gates can be split up into two types; the Action Stage gates and the Boss Gates.

The Action Stage gates are Gaia Gates that lead into the game's regular stages called Action Stages. The daytime stages where Sonic the Hedgehog is playable are colored orange and marked with a sun icon and can only be accessed during the day. Then there are the nighttime stages where Sonic the Werehog is playable, which are colored blue and marked with a moon icon and can only be accessed during the night. The Gaia Gates that lead to Action Stages, which are needed to progress the story, are automatically open when the story reaches the needed point, but there are also additional Gaia Gates that lead to non-story related Action Stages. These Gaia Gates can only be unlocked if the player collect enough sun medals or moon medals.

The Boss Gates are Gaia Gates that leads to specific level's boss fight, and are in the game's story the ones that take the user directly to the Gaia Temples. They are usually colored red and is marked with Dark Gaia's symbol. These Gaia Gates can only be unlocked once the player collects its Gaia Key, which is done by completing its local continent's nighttime and daytime stages.

PS2/Wii
In the PS2/Wii version, the Gaia Gates can be found on the local continent's hub world map, under the name Sacred Shrine and are the only hub areas on these versions that can be explored in 3D. The Gaia Gates presented here are large, ancient structures that remind a lot about the Gaia Temples, and each Gaia Gate has its own theme corresponding to the continent it represents (for example Holoska has ice all over the place). In order to gain access to the continent's Gaia Gate, the player has to talk to certain people in each town/village in order to obtain a Sun Tablet orMoon Tablet, which will then make the Sacred Shrine appear.

The Apotos Gaia Gate is the only one to be explored with Sonic. All of the other ones automatically transform Sonic into the Werehog upon entry.

Inside the Gaia Gate there are several doors that can be open in different ways. At the back of each Gaia Gate, there are up to three types of doors that lead to the game's Action Stages and Boss Stages.

The Action Stages are the game's regular levels and can be split up into Day Stages and Night Stages; the Day Stages where Sonic the Hedgehog is playable are marked with a sun icon and can only be open with a Sun Tablet, and the Night Stages where Sonic the Werehog is playable are marked with a moon icon and can only be open with a Moon Tablet. The doors that lead to the level's Boss Stage, and are in the game's story the ones that takes the user directly to the Gaia Temples, are marked with a star pattern and can only be unlocked with the Planet Tablet, which is obtained by completing the Day Stages and Night Stages. Note that not all Gaia Gates have all three doors. For example, Apotos does not have a boss, and Mazuri only has a boss.

There are also several additional doors found inside these Gaia Gates which can be can only be unlocked if the player collect enough sun medals or moon medals. The puzzles revolve around using (and at times avoiding) shafts of light that will transform the Werehog into Sonic. After a certain amount of time, Sonic will transform back into the Werehog. These doors will then reveal hidden rooms with puzzles, where the player can obtain hidden items such as extra lives, collectibles and bonus missions.

These versions' Gaia Gates are also all connected and the player can select another Gaia Gate by stepping on one of the glowing pads in the room to the left of each entrance.

Trivia

 * On the PS2/Wii version of Sonic Unleashed, Apotos is the only Gaia Gate that doesn't cause Sonic to transform into the Werehog in the main hall.
 * Playing with this reveals that it is not possible to cause the game to register a Drift bonus, even if drifting is utilized for an extended period of time.
 * Also, on the PS2/Wii Version of Sonic Unleashed, Eggmanland is the only location without a Gaia Gate.
 * In some of the Gaia Gate missions in the PS2/Wii version, Sonic is required to ring dash across certain gaps. The rings used here are unique as they regenerate shortly after being collected. This can be abused to gain boost power (though the boost is never needed).
 * This reveals that it is not possible to level up even if the ring quota to do so is met. However, three full bars of boost can be obtained.
 * Sonic can boost towards the screen. This is impossible in the regular day stages.
 * If Sonic transforms into the Werehog and back, he loses all his rings and boost.
 * A glitch exists in the PS2/Wii versions. If Sonic crawls around (during missions while he is in normal form) he will never change back to the Werehog. Even if the purple aura begins to show, crawling causes it to go away.