The logo for the London tube is a true design icon. Designed by Edward Johnston in 1918, the logo has remained relatively unaltered for nearly a century. Since then, cities around the world have developed underground, or in some cases above ground, modes of high-speed, mass transportation. With each city, comes a different logo, although many incorporate "M" into them because "Metro" is the most common term for the underground transportation throughout the world. Metrobits has a great overview of some of the different logos and what they represent.