The three young men set out, but they soon realized the futility of their search.  One of the brothers, Cadmus, consulted the oracle at Delphi and the oracle told him to abandon the search for Europa and to found a city.  To find the right place, he was to follow a cow until the animal sank down from weariness.

Cadmus travelled on until he reached a lush, fertile valley.  It was remote and unpopulated.  The cow lay down to chew the cud near a river, in a beautiful spot, and the young man decided that he would found his city in that very place.  Seeing that the prophecy had been fulfilled, he sacrificed the animal to the goddess Athena and then, overcome with exhaustion, he fell asleep.

A beautiful woman dressed in a white tunic appeared to him in his dreams.  She was wearing a helmet and a gleaming breastplate. In her hands she held a silver lance and shield, and on her shoulder was perched an owl.  Cadmus recognized the goddess Athena.  The apparition spoke softly to him:  'Cadmus, brave warrior, you must indeed found your city here.  To do so you must kill an enormous dragon who guards the Spring of ares.  Once you have vanquished him, pull out his teeth and plough a field to sow them.'

The boy prepared to fight the dragon who guarded the Spring of Ares, the god of war.  The brave warrior fought a terrible battle against the beast.  The powerful dragon used every possible trick, and Cadmus fought valiantly.  The ground was soaked with blood, and rocks went flying as though they were pebbles.  The yells of the hero and the roaring of the beast could be heard as far away as Mount Olympus, where the din of the contest disturbed the father of the gods who was resting.

Annoyed, Zeus sent his daughter Athena to help Cadmus, and put an end to this racket once and for all.  The goddess of war obediently appeared on the battlefield, but even with her help, it took Cadmus another day to defeat the powerful dragon.  After killing the beast, the hero pulled out his teeth.  He ploughed a field with great effort, sowed the teeth in the blood-stained and sweat-soaked soil, and waited.

Soon, from the dragon's teeth sprang many fierce warriors, who began to fight among themselves with uncommon determination until there were only five left.  The hero than attacked them and disarmed them.  The warriors who were called Sparti, 'sown men', then acclaimed Cadmus as their king and lord, and helped him build the walls of the city of Thebes.  Thanks to Athena's protection, the heroic Cadmus ruled from then on in that city, which was famous for the valor of her men, for they were born of a dragon's teeth.