Standing in water 14,750 feet (4,500 m) deep it is four miles (6.4 km) across at its widest point.

Mitiaro, also known as Nukuroa, is part of the Nga-Pu-Toru island group formerly, a volcano that became a coral atoll.

The island has been designated an Important Bird Area (IBA) by BirdLife International because it supports populations of Rimatara lorikeets and Cook reed warblers.

[6] According to oral tradition, Mitiaro was settled from Atiu, and was historically dominated by that island.

He left behind a Polynesian teacher, Taua, who began converting the islanders to Christianity.