That's how big the world of Avatar the Last Airbender is. Their world is 2106 miles from north to south pole, approximately. Ours is 7926 miles. How do I know this? Because in the episode where Aang and his friends first arrive at Ba Sing Se, someone says it used to take either "days" or "a few days" to walk from the inner wall to the outer wall. A man can walk about 36 miles in twelve hours, so three days would be about 108 miles. I took a scrap of paper, measured the distance from the inner wall to the outer wall on the big map, and then used that to measure the distance from the north to south pole. I got 2106 miles. The earth is three and three forths bigger than that, about 7126 miles. Their world is about the size of Mercury. It may not be completely accurate, but no one else seems to know, so that's the number I'm sticking with. :3