Before, the people believed the world was flat. However, Magellan proved that the world is spherical so he proved it by circumnavigating the world. Indeed, the world is round. It is because some masses of rocks had collided at each other, and thereby it was reformed.
The world is round because of the force of the environment around it while rotating to its own axis so all the top structure on Earth little by little were washed away and throw it away on some other places of the Earth the same as the other planet because of the rotation of it by its own axis and the revolution it made around the sunĀ