A Great Circle is the largest possible circle that can be drawn on the surface of a sphere, such as the Earth. It represents the shortest path between two points on the globe. For example, when flying from one city to another, airplanes often follow a Great Circle route to minimize travel distance and time. The concept of Great Circles is important in navigation and geography. The equator is the most well-known Great Circle, dividing the Earth into the Northern and Southern Hemispheres. Other examples include lines of longitude, which also form Great Circles, while lines of latitude, except for the equator, do not.