The idea of intelligence is explored in the concepts of computers (using bits as their basic units of information), whales (in their songs and their disruptions by human activities), DNA, the human brain (the evolution of the brain stem, frontal lobes, neurons, cerebral hemispheres, and corpus callosum under the Triune Brain Model), and man-made structures for collective intelligence (cities, libraries, books, computers, and satellites). The episode ends with speculation on alien intelligence and the information conveyed on the Voyager Golden Record.

Feast your eyes on a reconstruction of the mega-city and its amazing buildings. Alexandria, built in the middle of rancid marshland, had become in less than a century, the greatest city of the Mediterranean. An ideal position at the crossroads of east and west, and one that brought her great riches. Huge, modern, gleaming white and cosmopolitan, like no other in antiquity, it created its own identity.
While the beauty of its planning, its great arteries, its temples and its ports would be equalled only by its openness to the rest of the world. And the monumental achievements of its sovereigns, still shrouded in mystery, we'll never cease to fire our imagination for millennia to come.