In middle and high school, we learn that flat maps are distorted projections of a nearly spherical planet. They're always wrong. The popular Mercator map gets especially bad in the polar regions. Still, even with this knowledge, bad impressions form in our minds about the relative size of countries and continents. For example, though Greenland appears to be huge in a Mercator map, it's very small compared to the equatorial-centered continent of Africa.
This BuzzFeed video illustrates some of the common misconceptions and shows how big parts of the world really are.
-via The Presurfer