The Galactic Eterna Building (Japanese: ギンガハクタイビルGalactic Hakutai Building) is a Team Galactic's base of operations in Eterna City. As part of the plot of Pokémon Diamond, Pearl, and Platinum, the player must rescue Pokémon the villainous team has kidnapped. Before players can enter, the Forest Badge must be obtained,
so that HM01 (Cut) may be used outside of battle and the trees at the front of the building can be cut down.
The Galactic building has four stories; each contains members of Team Galactic that must be defeated to progress.
The sign outside the building reads:
Team Galactic Eterna Building
We Want Your Pokémon!
The Galactic Eterna Building as it appears in Pokémon Diamond and Pearl
The player enters Galactic Eterna Building to save Rad Rickshaw's Clefairy, and other Pokémon that Team Galactic have stolen from the residents of Eterna City. It is a compulsory part of the game; defeating the henchmen and Commander Jupiter in battle will rescue Rad's Clefairy, and he will give the player a Bicycle as thanks.
The player will then be able to cycle down Route 206's Cycling Road.
In Platinum, a player with the Secret Key in their possession can unlock a hidden room containing five appliances that can change Rotom's current form. The room is located on the ground floor, to the left of the television.
It also contains a notebook with all of the details about changing Rotom's form and when it will revert automatically back to the normal form. The notebook appears to have been written by Charon.
Team Galactic 
