The Realm of the Canopy actually lies within the boarders of the Empire of Miradorium. However it's technically its own separate political entity with its own race of people, the Prangels, customs and rulers. However, those rulers pay heavy tribute to the Emperor of Miradorium to assure their independence.
The Realm of the Canopy consists only of a canopy of a forests of gigantic trees that grow within the empire of Miradorium. These gigantic trees known as Magnum Arbours are large enough that a whole civilisation including buildings and walkways can exist within its branches.
The Realm of the Canopy is the smallest of the 'independent' realms.