A long time ago, perhaps in Middle Ages or in Renaissance... before the Enlightenment Period, people believed that the Earth is flat. They wanted toreach the sky. The moon, the sun, and the stars were thought to be hanging somewhere above, at the top of the sky.
People believed that they live in some sort of a bowl. If they really really wanted, they could reach the sky. That's where the story of Babel kicks in. People started building a tall tower to reach the top of this world.
This picture is about them - from the past and their perception of the world.