You are at a point on Earth. You travel exactly 100 miles due south. You turn and travel exactly 100 miles due west. You then turn and travel exactly 100 miles due north. You notice that you are now exactly at the point from which you started. Where are you at the beginning and the end of the trip? Are there any other points on Earth where this can happen? If so, where are they?

The question you posed is a famous brainteaser. It is often used in the technology industry. The key idea to grasp in this question is that the earth is a sphere. Therefore, if a person is at the North Pole and travels 100 miles to the south, then heads 100 miles to the west, and then travels 100 miles to the north, the person would be at the North Pole. The travel route will actually look triangular in shape.
There are many other answers to this question. Actually, there is an infinite number of answers and they all involve traveling near the South Pole. In this situation, think of a circle 100 miles in circumference near the South Pole. If a person starts 100 miles north of this point, then travels 100 miles to the south, followed by 100 miles to the west, and then goes 100 miles to the north, you will end up where you began. There is an infinite number of points a person can start from this line of latitude and end up in the same place. The travel route will be circular in shape.
If you click here, you will go to a page that has a YouTube video that explains this process in detail.
https://mindyourdecisions.com/blog/2011/02/22/one-mile-south-one-mile-east-one-mile-north-a-classic-puzzle/