This is another old puzzle, but not so well known as it should be.
A hiker leaves his tent and walks five miles due south, turns and walks five miles due east, and finally walks five miles due north. You would expect the walker to have a further trek of five miles due west in order to get back to the tent.
Oddly, the hiker is back at the tent.
How is this possible?
The only way that this is possible is if the tent is at the North Pole.
The hiker walks five miles away from the pole (which must be south), then walks east along a line of latitude that is five miles from the pole, and finally walks five miles north back to the pole.