I used to believe that the borders of countries would have actual "lines" or "walls" on the ground to signify that you were entering a new country.
A childhood belief about places

others believed things like this
- I used to believe that the moon was another country and that all countries were little planets.Anon
- I used to believe that thunder was aliens entering the atmosphere, and lightning was them firing lazers at us!— Zeepoo-zoop
- I thought ground beef was the meat they scraped off the ground at the slaughterhouse. Yuck.Anon
- I used to think wars started when a sergeant from one country socked a sergeant from another country.— recovering
- I used to believe that clouds were foreign countries.— Ade
- I used to think the "Cold War" was a war where countries tried to freeze each other to win the war. Anon