Metru Nui

In the Bionicle storyline, Metru Nui is a huge island city located far beneath the surface of the island of Mata Nui. It was the original home of the Matoran prior to their emigration to Mata Nui. Metru Nui sits in the center of a vast silver sea of liquid Protodermis. The city is divided into six districts, or "Metru": Ta-Metru, Ga-Metru, Onu-Metru, Po-Metru, Le-Metru, and Ko-Metru. Each Metru's Matoran play a different role in the smooth running of the city. In Ta-Metru, Matoran make Kanohi from Kanoka. In Ga-Metru, liquid protodermis is purified so the Ta-Matoran could use it. In Po-Metru, Matoran built sculptures. In Ko-Metru, Matoran look into the future. In Onu- Metru, there are places called Archives where Matoran honour the past. The Metru are connected to each other by a complex system of transport chutes run in Le-Metru.

Some of the most important sites in Metru Nui include the Coliseum, sports center and power source for the city; the Great Furnace in Ta-Metru; the Great Temple in Ga-Metru; the Onu-Metru Archives; the Moto-hub in Le-Metru; the Sculpture Field in Po-Metru; and the Knowledge Towers of Ko-Metru. Metru Nui is ruled by Turaga Dume, and protected by robotic order enforcement squads called Vahki. Each Metru has a different type of Vahki, but all are highly efficient and relentless enforcers of the laws of the city.

Metru Nui is currently destroyed by an earthquake, and many Rahi have escaped from the Archives in Onu – Metru. Also, the Visorak has arrived in Metru Nui.