Here are locations other than the 4 main ones.

Maliria : Maliria was once the fifth main location of the world. It desapeared under the ocean after the 2nd Great War of Shadows. This place was inhabited by Iraz and his servant.

The Island of Shadows : The second base of Iraz, this island has 12 floors filled with different task to do and creatures to defeat.

Kingdom of Light : Once seen as a refuge for the matoran and agori, this location is now nothing but ruins.

Maya-nui : An island inhabited by matorans, Toa and other species.
Homeland of an organisation names the Order of Justice.

Kaya-nui : A tropical island inhabited by an organisation called the Guardians.

Neka-nui : A city like Metru-nui of the Matoran Universe.

Tava-nui : An island, homeland of a group named "The Legion of Agten".