Ko-Koro

"Turaga Nuju's village is called Ko-Koro. It's tucked away under a huge, solid ice block dividing two glaciers, safe from dangerous avalanches and icy storms. In the snow-covered mountains surrounding the village, deadly glacier crevasse can swallow the unwary. It's a cold, dangerous region. Kopaka makes his home in the area surrounding the village."

- BIONICLE.com

Ko-Koro was the village of the Ko-Matoran on Mata Nui.

History
The location of Ko-Koro was chosen by Toa Nuju after the events of the Great Cataclysm, when the Ko-Matoran were awakened by the Turaga. The Ko-Matoran, led by Nuju, traveled midwest until arriving on Mount Ihu and founding a village near its peak.

Quest for the Masks
After a year of peace on Mata Nui, the village began suffering from Teridax's infected Rahi attacks. The constant harassment continued for many centuries. However, the Ko-Matoran were able to defend themselves from the Rahi until the arrival of the Toa Mata. Toa Kopaka soon arrived in the village and went into Mangaia with the other Toa Mata to fight Teridax. The Rahi attacks ceased after his defeat.

Bohrok War / Rahkshi
When the Bohrok swarms were awakened by Makuta, a swarm of Tahnok arrived in Ko-Koro, partially destroying it. After the war, however, the damaged section of Ko-Koro was reconstructed.

After the imprisonment of the Bahrag, Nuhvok-Kal and Kohrak-Kal attacked the village, stealing Kopaka's Nuva Symbol from the village's Suva. The symbol was later recovered and returned to the Suva.

Ko-Koro was damaged while the Rahkshi were searching for the Avohkii. After Metru Nui was rediscovered the Ko-Matoran departed, leaving Ko-Koro abandoned.

It was eventually destroyed by the Bohrok once the Toa Nuva freed the Bahrag.

Landscape
Ko-Koro was located in the forbidding landscape of Ko-Wahi, where it was hidden beneath an enormous chunk of solid ice that separated two glaciers and surrounded by large crevasses. The village itself had a single gate facing a massive crevasse, which was guarded at all times by the Sanctum Guard. The only other known entrance was a tunnel that led from the Sanctum to the Drifts. Inside the village, the Matoran lived in either huts built of ice on the ground, or in rooms carved into the glaciers that surrounded the village.

The most famous location in Ko-Koro was the Sanctum, which contained the Wall of Prophecy.