With 1,400 years of often-troubled history, it's a wonder London's St. Paul's Cathedral is home to only one ghost.

Many cathedral visitors have reported seeing the hazy form of a clergyman with long, gray hair and flowing robes gliding through one of the massive building's memorial chapels. Always following the same path, the ghost—dubbed "Whistler" for the somber tune he emits—moves slowly through the chapel and disappears into a wall near the room's entrance. Renovations in 1918 revealed that behind this section of wall rises a small, abandoned staircase leading to a room deep within the cathedral that no one knew existed.