Aqua Nui

Aqua Nui was a legendary underwater city that stood on today's Mahri Nui. It was destroyed during The Battle of Aqua Nui.

Origin
It is said that the Great Beings laid the foundations for Aqua Nui. It was built upon The Staff of Nui which the Great Beings had hidden from any danger. The newly-created Matoran were placed in it to live and work there.

The Battle of Aqua Nui
Life went well for the Matoran of Aqua Nui until Makuta Teridax led his fellow Makuta to retrieve the Staff of Nui. They promised not to hurt the Matoran, but Teridax had secretly captured six Matoran, Wole, Toa Cjjj to mutate and use as servants of the Brotherhood of Makuta. But the Great Spirit knew this and transformed them into the [[Toa Aqua.

After freeing themselves, the Toa went to fight the Makuta.