WONDERBIRD, certainly an unbelievably refined cartoon, drawn in a deliciously oldfashioned way, and sensationally oldfashioned in almost any respect, takes place in a kingdom ruled by a mean and heinous monarch; accordingly, the kingdom, or at least what we seethe surroundings of the king's palace, seems devoid, uninhabited.
A few inhabitants there areaway from the Sunin the withered underground city.
An advicecall it an allegory, call it a parable, only do not call it a fable.
Because IMDb encourages prolixity, and maybe for other reasons as well, I will add that this cartoon is the work of the great Paul Grimault.