Gaia Gates serve as the explorable hub areas in the PS2 and Wii versions of Sonic Unleashed. Talking to certain townsfolk in each village will earn the player a tablet, granting him or her access to that continent's Gaia Gate. From there the player can then enter a stage or find items hidden in each room of the Gaia Gate. Sun Tablets unlock day stages, Moon Tablets unlock night stages, and Planet Tablets unlock boss battles. To find hidden items such as extra lives and bonus missions, the player must have enough sun and moon medals to open a door in the Gaia Gate. Upon collecting all of the items in a room behind one of the doors, a small notification will appear onscreen.
Every Gaia Gate has its own theme corresponding to the continent it represents. The gates are all connected and the player can select another gate by stepping on one of the glowing pads in the room to the left of each gate. Apotos is the only Gaia Gate that doesn't cause Sonic to transform into the Werehog in the lobby area, while Eggmanland is the only continent that lacks a Gaia Gate entirely.