Perhaps the most famous Dane is actually Hamlet, the title character of William Shakespeare's famous play, which was set in the real castle of Kronborg in Helsingør, north of Copenhagen. The play was based on an old Danish myth of the Viking Prince Amled of Jutland, and his quest for revenge against his father's killer. Another widely known Dane is Hans Christian Andersen, an author mostly famous for such fairy tales as "The Little Mermaid", and "The Ugly Duckling". Also Karen Blixen, Tycho Brahe and the philosopher Søren Kierkegaard are well-known worldwide. There are many famous Danish scientists, including Niels Bohr, the famous physicist who developed the first working model for the atom, and Ole Rømer, who discovered the speed of light. Hans Kirk, although less well-known outside of Denmark, is the author of the best-selling Danish novel of all time, "The Fishermen".