On Creating Worlds

I am currently reading Dune by Frank Herbert and I'm amazed by how vivid the world of the story is. As a writer, one of my goals is to do just that, create a world with its own magic, politics and religion. This is no easy task, but details make a story greater, and convince the reader that the world is probable. 

For examples, I turn to Tolkien, who created languages, histories, races and magic to make an epic story. J.K. Rowling invented her own system of magic, and a whole dimension of magic away from the "muggle" world. Diana Wynne Jones created a familiar yet different world related to the European countries.
After reading many  of these stories, I wonder what makes the world of a book seem real. Some would say the characters and their way of living life can reveal a world through human eyes. Others agree that the geography and history of the world makes it realistic to a reader. Magic and languages must be carefully crafted. Myth and folklore add a dimension to the world of a story and create an importance of their own.
Many of my inspiration for writing comes from stories with vivid and realistic worlds.The worlds of Final Fantasy with their elements of myth and folklore become very real while you learn their stories. Spira, from Final Fantasy X, was one of the most amazing and vivid worlds I have ever seen. Coccoon and Pulse from Final Fantasy XIII were also detailed worlds with Steam Punk flare. Another world I admire is the world of Avatar the Last Airbender. Not only did this world have it's own magic. It had its own myths, animals and a religion that played a key part of the story. In the Stravaganza Series by Mary Hoffman, she creates her own Italy with beautiful and intriguing detail, including important magical props.
My current story is a world I have created in the example of these stories. I don't have languages, but one of my stories does have a language I invented. 
I want to create the feeling of stepping into a new world. Like when Jake Sully becomes a Navi in the film Avatar. The vivid and memorable landscape, and the interesting culture of the Navi makes the world of Pandora an amazing element of the film.
Creating worlds, for a writer, is no easy task. Details must be added. A history invented, and characters introduced before a story can really feel like a journey.

What elements do you think create worlds in stories?

The Stravaganza Series: City of Ships

Around Junior year of High School I discovered a book called The City of Masks by Mary Hoffman. It was one of the many books in a series called Stravaganza. Hoffman has created an alternate universe which mirrors the country of Italy. In Talia gold is silver and a hero is always needed. The city of Bellezza is a mirrored Venice governed by a powerful and clever Duchessa. Remora is an alternate Siena with sections dedicated to the Stellata, a race with a jockey representing each constellation in the zodiac. Giglia is Talia's Florence and contains a labyrinth in a monestary called Saint Mary among the Vines. Padavia, the twin of Padua houses the Scriptorium, the renaissance printing press, forbidden to publish certain scientific texts. All this and a brush of Talian politics opens the realm into City of Ships. This new novel takes place in Classe, the Talian Ravenna with a new protagonist named Isabel. Hoffman's series is filled with imagination as adventure and mirrored historical details unfold in the world of Talia. The author's writing inspires me to create a world of my own.

For more information, here's the official website for the Stravagante:
Stravaganza