As you are aware, though in general one
gives no thought to it, the world is a place of infinite variety
and richness. In it you have magnificent cities, filled with mingled
voices and fabled treasures, you have royal palaces, hovels,
mountains enchanting and drear, murmuring groves, tranquil lakes,
torrid deserts and the endless snows of the North.

what is the meaning of "mingled voices" in this sentence?