"This is my favorite of the seven Narnia stories," Barnes, who reprises his role as Caspian, tells PEOPLE. "I remember reading it as a kid and imagining all this powerful imagery of the ship and all the characters. To see them real in front of my eyes is so surreal."
In the third film based on C. S. Lewis's popular books, and due in theaters Dec. 10, Lucy (Georgie Henley) and Edmund Pevensie (Skandar Keynes) return to Narnia with their cousin Eustace (Will Poulter) to help Caspian (Barnes) find seven lords while aboard the Dawn Treader ship.
Along the way they encounter a star in human form and a magical pond that turns anything into gold.
"The story is a voyage of self discovery that has a lot of magic, adventure and romance," says the handsome British actor. "It's got that fairytale adventure feel to it and the excitement of the first film."