It's red, octagonal, and people stop when they see one almost anywhere on the planet.
The familiar stop sign is the most widely recognized road sign in the world. In 1949, the United Nations began working on an international system of road signs so tourists and truck drivers could safely travel the streets of foreign lands. Step 1 was to abolish printed words on traffic signs in favor of shapes and colors.
The stop sign was an exception. The UN decided that the shape was so familiar that it didn't matter what was written across it. So in France it reads "Arrt"; it's "Alto" in Mexico, and "Stop" in the United States.
A handful of countries - including Japan - decline to use the international sign system exclusively.