The county seat was at the main settlement, Tasiilaq.
[1] In 1974, the Northeast Greenland National Park was created from the vast and virtually uninhabited northern part of Illoqqortoormiut Municipality.
Tunu was bordered in the east by the Greenland Sea, Denmark Strait and the North Atlantic Ocean.
To the west lies Kitaa, and to the north, Avannaa.
In 1988, the National Park was enlarged into Avannaa (North Greenland).