Albus Dumbledore in the 'Harry Potter' novels has a scar above his left knee that is shaped like what?

According to the 'Harry Potter' series by J. K. Rowling, which has been adapted into several films, Professor Albus Dumbledore claims to have a scar above his left knee in the precise shape of a map of the London Underground. The map is a diagram of the underground train lines in the English capital city. It is never revealed how Dumbledore acquired this scar.

Albus Percival Wulfric Brian Dumbledore, to give him his full name, was the headmaster of Hogwarts School of Witchcraft and Wizardry until his death in 1996. He was the headmaster of the school during the majority of the titular character's school days. In the 'Harry Potter' films, Dumbledore was first played by Richard Harris, and then by Michael Gambon after Harris died.

'Harry Potter' is a series of seven fantasy novels written between 1997 and 2007. Each book tells the story of one year of Harry's life at Hogwarts School of Witchcraft and Wizardry, which he attends with his best friends, Ron Weasley and Hermione Granger. Throughout the series, an evil wizard known as Lord Voldemort tries to kill Harry several times, after having failed to kill him as a child. According to a prophecy, Harry would grow up to kill Voldemort, which he is desperate to prevent.