The Matoran Universe

There are many islands in the Matoran Universe.
Mata Nui, Metru Nui, Karzahni, Xia, Zakaz, Odina, Northern Continent, Southern Continent (Voya Nui, Mahri Nui), Karda Nui, Destral, Daxia, Stelt, Artakha's Island, Tren Krom's island, Nynrah, Visorak, The Pit, Southern Islands (Artidax, Keetongu and Tahtorak's homeland)
All of these islands are inhabited by many beings ranging from Matoran to Rahi to Tren Krom himself.

The Island of Mata Nui is a massive island on the ocean moon of Aqua magna. When the Visorak took over the island of Metru Nui, the six Toa Metru evacuated the Matoran of Metru Nui to a new island they had found. They named this island Mata Nui in honor of the Great Spirit. The Turaga each claimed a Wahi, or region, to build their villages on. The villages were built in the elemental region that they corresponded with. Ta-Wahi (Fire), Ga-Wahi (Water), Le-Wahi (Air), Ko-Wahi (Ice), Onu-Wahi (Earth), and Po-Wahi (Stone). Each of the Toa Mata landed in their Toa Canisters on the beach of their respective Wahi and set out to find their Koro (village)

Metru Nui is an island that has been completely covered in a mega-city. Each of the elements (Fire, Air, Water, Stone, Earth, Ice) has it's own district. The districts each have their own function in the city. Ta-Metru, is where the mask makers worked. The great Ta-Metru forge is where different types of Kanoka disks are made and programmed to either be used in mask making, or recreation. Ko-Metru is were the Ko-Matoran scholars study and learn in the huge towers made of Knowledge Crystals. Onu-Metru houses the extensive Onu-Metru Archives. Here is where the Onu-Matoran store and catalog all of the information they know about the universe, including ancient stone tablets and all types of Rahi imaginable. Le-Metru is in charge of the transportation in the city with the Moto-Hub, the biggest chute station on the entire island, and the Le-Matoran also invent all kinds of new technology. The chute system of Metru Nui is a network of air-filled and magnetically powered tubes that run throughout the city. Matoran also use airships, Moto-Sleds, and a variety of other modes of transportation. Ga-Metru is the center for learning in the city, and it is where all of the schools and science labs are situated. Ga-Metru also is where Liquid Protodermis is extracted from the silver sea and purified for use in the other Metrus. And finally Po-Metru is where the artisans and craftsmen build great statues out of stone in the Po-Metru Sculpture Fields. The Coliseum is the center of Metru Nui and is where sporting events like Akilini and Kolhii are played. It is also where the Turaga live and govern the city from.

Karzahni is a land ruled by the being Karzahni. Broken Matoran were sent there to be repaired. Matoran legend, however portrayed it as a land where the lazy and poor Matoran were brought to be tortured. The land of Karzahni was created by the Great Beings for the being Karzahni to repair damaged and then to send them back to where they came from. Some of the geographical features of Karzahni are volcanoes that spew ice, waterfalls made of dust, and if a Matoran sat down, the rock he was sitting on turned him into a statue.

Xia is an island created by the Great Beings that became environmentally devastated by all of the industry covering the island. The Vortixx inhabited Xia and they specielized in making weapons. All of the organizations in the Bionicle universe were supplied at one point by the Vortixx. Another strange inhabitant of Xia is something called "The Mountain". This being is actually a sentient rock. It has the ability do devour climbers without warning, and it would grow whenever it ate. Part of the Vortixx rite of passage was to climb The Mountain. The climber traveled in pairs and were especially respected if they returned alone.

Zakaz is an island inhabited by the Skakdi. Zakaz was once a tropical island paradise, but was eventually turned into a complete ruin. Makuta Spirah tampered with the Skakdi and gave them elemental powers like Toa and vision. These enhancements made the Skakdi, an already brutal people, even worse. Spirah eventually left Zakaz and put the Visorak in charge of the island. The Visorak were eventually overthrown by the Skakdi and the Skakdi began fighting a massive civil war.

Odina is the center of control for the Dark Hunters. They chose it because of it's geography, which helped barricade the island. The massive mountains that surrounded the island made it very hard to breach and the island itself was situated very far from any Matoran trading routes. The main buildings on this island are those of the Dark Hunter Fortress. It serves as a training ground for Dark Hunters.