Large Mobile Cities created by humans to live after the earth atmosphere became too polluted to live, are called Regios. Built with a circular foundation for its inhabitants, a city is also surrounded by numerous, huge legs for mobility. Atop of the legs is an air-filter, a membrane of air that covers the city to protect any invasion of contaminants. There is also the mention of Selenium, a special ore that needs to be replenished and has many Regios fight each other for its survivability. Each city is named after the Electronic Fairy that controls the Regios. Most Regios avoid Filth Monsters(aka Contaminoids) as much as possible but with the exception of one city, Glendan, which does the opposite as it constantly finds monsters.
There are two different kinds of cities; Academic Cities & General Cities.
- Academic Cities like Myath and Zuellni, are where students from different cities come to learn & study. More than half of the population are students and rarely adults. The functions of an academic city, for example, administration and operation, are relied on the students. Education wise, seniors oversee the tuition of the juniors. Most Academic Cities are members of an alliance known as the Academic Union, which sponsors the InterCity Matches. Whereby, the condition to either win or lose the match, is determined when the city's flag is seized.
- General Cities are the main cities where most of the population live.
Due to a treaty, only Regios of the same type are allowed to have a match with each other.
- Proto-City Lance Shelled Glendan: The most powerful city in the world due to its regular encounters with Filth Monsters of all levels and was the birthplace of the Military Arts, which most other cities practice today. The Twelve Heaven's Blades are found here under the command of the Glendan Royal Family.
- Academic City Zuellni: A city governed by its Students Council President and part of the Academic Cities Union. This is where the manga/light novel/anime takes place. Its population is 60,000 and has a six year system, offering education in General Studies and Martial Arts Studies. Inter-Platoon Tournaments are huge events, much like a simulated form of the InterCity-Match. FanClubs are also formed for popular platoon members. Trams are used for transport within the city. Its Electronic Fairy takes the shape of a pale blue, young girl.
- Academic City Gandoweria: A former city that was overrun by Pollutant Beasts not long after their victory over Zuellni two years ago. Its Electronic Fairy takes the form of an goat-like creature and is currently running amok as a Haikizoku .
- Sheniebel: AKA 'Fairy Nightingale City', it is the city Nina Antalk and Harley Sutton grew up in and is currently the only city with the "Riggzario Engine", which is capable of producing new Electronic Fairies with its artificial uterus-like system. Like Glendan, Sheniebel also has a royal family, which Nina is the heiress of, as seen in the manga of Chrome Shelled Regios. Besides that, this city is also known to have Fairy Hunters who predate for money.
- Academic City Myath: Its Electronic Fairy takes the form of a red bird. In the anime, the military capabilities of this city are shown to be poor and perhaps even worse than that of Zuellni. No resistance was shown from the city when it was attacked by a mature filth monster.
- Transport City Yoltem: According to the manga, this is the original home city of Mayshen Torinden, Mifi Rotten and Gerni Naruki. All roaming buses eventually return to Yoltem and most travelers will encounter it during their travels. Only its Electronic Fairy knows the current location of every regios.
- Trade City Santo Brug: The city Kalian Loss and his sister Felli grew up in. Their family holds significant positions and weight in the city.
- Velzenheim: Dixerio Maskane's place of origin. Originally known as Gravel Sand City, it was later known as Avarice City due to the Maskane family. After the city's fall, its Haikizoku dwells within Dixerio.
These are used for commuting between cities. Roaming buses commute to various cities daily. It is also designed with the purpose of trade in mind. Since travelling outside of the cities is prone to the danger of attacks by Filth Monsters, a detour or a stop for several days are employed. Regardless of the final destination of all roaming buses, it is necessary to travel via Yoltem. However, due to the risk and inconvenience of travelling, most people do not travel to other cities. If the need to travel arises for the purpose of trade between cities, there is the alternative of a caravan.