Metru Nui (Echo 1)

"Then it will surely be a "city of legends," since, as you know, most legends are about the dead!"

- The Shadowed One during the Toa-Dark Hunter War.

Metru Nui is a bustling ecumineopolis on the island of the same name.

Landscape
As stated before, Metru Nui is an ecumineopolis (an "all-consuming city") covering the island for which it was named. After the Matoran Civil War, the Matoran separated into six separate districts, where certain industries were centered. Canals were built in between each district to allow easy access to the Coliseum, the massive building which resided at the center of the city.

Districts
Metru Nui is separated into six separate districts, each named according to the most abundant element in it.

Ta-Metru
Ta-Metru is a fiery district, and is noted for its numerous factories and foundries. Ta-Metru is the powerhouse for mask manufacturing in Metru Nui, and is also known for refining materials mined from Onu and Po-Metru.

It is primarily populated by Ta-Matoran.

Ga-Metru
Ga-Metru is Metru Nui's center of learning and religion. The district is adorned with schools, work places, and temples to Mata Nui. Its primary industry is protodermis purification, in which the raw silvery liquid from Metru Nui's surrounding ocean is taken and purified into a glistening new liquid. The protodermis is then transported to Ta-Metru for disk and mask manufacturing, although Ga-Metru does its fair share of manufacture as well.

The district is primarily populated by Ga-Matoran, but there are small communities of Ce-Matoran and Matoran of Lightning.

Le-Metru
Le-Metru is the transportation powerhouse of Metru Nui, producing every vehicle in the city and maintaining the complex network of transport chutes. They also transport goods via airship. The district is also known for being the city's "entertainment district," as it is filled with bars, clubs, and theaters were off-duty Matoran can enjoy themselves.

The district is mostly populated by Le-Matoran, but also has a small population of Matoran of the Green.

Ko-Metru
Ko-Metru has very little industry, and focuses more on philosphy and prophecy. The district is dominated by knowledge towers-- massive, crystalline structures where Matoran work to derive the will of Mata Nui from the stars in the night sky. The district is known for being in constant silence.

The district is populated by Ko-Matoran and De-Matoran and rarely has travelers.

Po-Metru
Po-Metru is the center for tool manufacture and artwork in Metru Nui. Sculpture work is extremely popular in the district. Po-Metru also does a lot of protodermis mining, and has a steady stream of trade to Ta-Metru for mineral refinement.

The district is predominantly populated by Po-Matoran, but there are some Onu-Matoran that live in the sub-city. It also has small communities of Fe-Matoran.

Onu-Metru
Onu-Metru's surface district is quite small, but the underground portion honeycombs the entire city of Metru Nui and extends out into the sea. Onu-Metru is the district that maintains all of Metru Nui's complex sewer, heating, air conditioning, and power systems. The district is also home to the Archives, a massive museum with displays of every Rahi, artifact, and mask ever discovered.

The district is primarily populated by Onu-Matoran, but also has a small population of Ba-Matoran.

Population
Metru Nui is the city of the Matoran, and they are the most populous species on the island. But there are other species inhabiting the city.

The Matoran
The Matoran are the primary species inhabiting the island. The Matoran there before the evacuation of the city had different armor than what they had before the Great Cataclysm. This was on account of having degraded by their time in Matoran Spheres during the aftermath of the Great Cataclysm. Before returning to the city they were taught to rebuild themselves, so they had bodies akin to their earlier forms even if their current armor varies.

Many Matoran had recently escaped to Metru Nui from Karzahni with the assistance of the Toa Nuva, as well as the Av-Matoran from Karda Nui. Later on, all of the Matoran evacuated to the surface of Spherus Magna.

Turaga
The Turaga were the leaders of Metru Nui. There were seven Turaga in Metru Nui: Dume, Vakama, Nokama, Matau, Whenua, Nuju and Onewa. The last six Turaga were once Matoran inhabitants of the city and later Toa Metru during the time leading up to the Great Cataclysm. There was also at least one other Turaga that led the city before Dume. The Turaga emigrated to the surface of Spherus Magna due to massive damage caused to Metru Nui.

Toa
The Toa were the main protectors of Metru Nui, though before the second appearance of the Kanohi Dragon, there was no need for them. Metru Nui once even hosted over 300 Toa. Throughout history, it was protected by the Toa Mangai, the Toa Metru, the Toa Nuva, Toa Takanuva, the Toa Mahri (excluding Matoro) and most recently, the Toa Hagah. Metru Nui was guarded by the Toa Hagah and Gali Nuva until they evacuated to the surface of Spherus Magna due to the damage done to the city.

Rahi
There were many species of Rahi living on Metru Nui, including some driven there by the Visorak horde. Some of the Matoran of Metru Nui kept tame Rahi as pets, although a Rahi larger than half a bio could not be kept in a private residence under Metru Nui law. Due to massive damage to Metru Nui, all the Rahi performed a mass exodus to the surface of Spherus Magna.

Trivia

 * This is Echo 1's version of the real island in the BIONICLE canon.
 * Some information was imported from BS01.