Thousands of years ago, according to the Old Testament, the Jews were slaves in Egypt. The Israelites had been in Egypt for generations, but now that they had become so numerous, the Pharaoh feared their presence. He feared that one day the Isrealites would turn against the Egyptians. Gradually and stealthily, he forced them to become his slaves.
He made the slaves build grand 'treasure cities', as shown in the picture. The Egyptian overseer in red, holding a stick, is giving instructions to the barefoot slaves, who are building a wall. In the left hand picture, the overseer keeps watch on top of a tower, while the slaves make bricks from clay and straw.