In Genesis, humanity tries to build a tower to heaven, and God scatters them by giving them different languages. Bruegel set the story in a Flemish port, and his tower is modeled on the Colosseum in Rome, which he had seen on his travels.

Look for the details of the construction: cranes driven by men walking inside treadwheels, scaffolding and stonemasons, and in the lower left King Nimrod inspecting the work while workers kneel before him.