"Part of the attraction of the Lord of the Rings is, I think, due to the glimpses of a large history in the background: an attraction like that of viewing far off an unvisited island, or seeing the towers of a distant city gleaming in a sunlit mist. To go there is to destroy the magic, unless new unattainable vistas are again revealed."
-- J. R. R. Tolkien, Godfather of World Building
The secret to creating a compelling world is to maintain the illusion that there is always more.
The second biggest mistake amateur world-builders make when showing off their world is to explore all of it. The worst is when they let the narrator or the protagonist or, God forbid, some professor character infodump all over the reader about their beautiful world -- all its countries and cultures, its languages and latitudes.
But even those that avoid the infodump -- who take their protagonist through the world so the reader can experience it -- will sometimes make the mistake of showing everything.
As the author, you need to know everything about your world, precisely because of what Tolkien says above. The reader wants hints that the world is much bigger than what they see. And if you always "go there," if you tell them all about it, you destroy the magic.
The Hunger Games still has districts we know nothing about. Mistborn implies the existence of undiscovered metals, with undiscovered powers. Even if you've read everything the Tolkien estate has ever published, there are still places in Middle Earth that you've only heard about. That is what will make your world compelling.
What are your favorite fictional worlds? What parts do you wish you could see more of?