Gamma City is located deep underground and the only way to get there is by a special elevator. Right below the city is an underground pool of lava. It is not inhabited by anyone instead, it is a research facility for Mechanical Bakugan. This was the place where Cyborg Helios and Hades were made. Once Dan Kuso and Ace Grit destroyed their Dimension Controller, however, the building started to come down and the place was evacuated with the debris being burned by the lava.