Fun Riddle

Many people who like logic riddles have probably already heard this classic: "You are standing at a point on earth surface. You walk 1 mile South, 1 mile East, and 1 mile north. You end up where you started. Where are you?" This fun riddle actually has many answers. To be more precise, it has infinitely many solutions. To correctly answer my riddle, define the set of all points on earth's surface for which the above statement is true. The first person to comment the entire correct answer will receive all the rewards of this post. Enjoy!