Teppelin

Teppelin (テッペリン) is the beastmen headquarters and the residence of Lordgenome. It is a large Groove-shaped fortress that breaks the cloud barrier. Contained within it is the Space Gunmen, Dekabutsu.

History
Little is known about the city itself. Only that after the end of the First Anti-Groove War, and following the beginning of Humanity living underground, Lordgenome began creating the Beastmen to serve him in keeping Humanity from exceeding a population of 1,000,000 and setting off the Human Extermination System set up by the Anti-Grooves. For the following 1,000 years, the Groove King began to take in women from a certain village in order to produce children to raise and later abandon/discard from Teppelin (the last of these children was a daughter named Nia), it was around this time that a small band of Humans managed to find a means to fight back against the Beastmen by stealing Gunmen and stormed against Teppelin itself after defeating each  of  the  Four  Generals along the way there. It was during the 7th day of the Battle of Teppelin that the Groove King was killed by the  leader of Team Dai-Gurren when Teppelin fell. Over the next seven years, a new capitol city was built on the ruins of Teppelin.

Trivia

 * In the Otoko Series, it is referred to as the Teppelin Foundation (テッペリン財団), and is an American corporation which produces Gunmen in an effort to forcefully subjugate Japan.