The planet Majipoor, as described in Robert Silverberg's series of fantasy/sci-fi books.
Renowned science-fiction writer Robert Silverberg wrote a series of books, all playing on the same world, with a rich set of intelligent species living together in a cosmopolitan way.
These books are:
Lord Valentine's Castle
The Majipoor Chronicles
The Mountains of Majipoor
The Sorcerers of Majipoor
Geographical structure of Majipoor:
Three major continents: Alhanroel (heavily populated, political and cultural center), Zimroel (mostly agricultural) and Suvrael (mostly deserts and high temperatures, sparsely populated)
Political structure of Majipoor:
A supreme ruler (the Pontifex), located in the "Labyrinth", a vast underground city, with a large bureaucratic staff.
A public leader (the Coronal), holding the title "Lord", living in a vast castle at the top of the enormous mountain called Castle Mount. A moral control figure, (the King of Dreams), uses a telepathy machine to enter the dreams of criminal people and punish them. A psychological assistant figure, the Lady of the Isle, uses a similar telepathic device to offer moral assistance and give comfort to the people of Majipoor. The Lady of the Isle usually is the mother of the Coronal.
When a Pontifex dies, the Coronal becomes the new Pontifex, and has to elect one of the princes living on Castle Mount as new Coronal.
Species on Majipoor:
Humans (coming from Earth, several thousand years ago)
Skandars (huge beings with four arms)
Ghayrogs (reptile species)
Vroons (small gnomes with tentacles)
Hjorts (leathery humanoids suited to extreme climate conditions)
Shapeshifters or metamorphs (the only intelligent species native to Majipoor. They have been nearly exterminated by the other inhabitants and restricted to a reservation)