According to the legend...
Long ago in a cave at the bottom of Wawel Hill, there once lived a terrible dragon. This dragon did whatever he wanted to. Every week the dragon appeared and stole of a cow. The king wanted this dragon destroyed. He invited knights and noblemen to come and slag the dragon, promising that whichever one killed the dragon could be rich.
The populace made many attempts to kill the dragon but nothing successed and many of those that attempted were killed. One day, a young, poor shoemaker's- call Dratewka- asked the king if he could try to slag the dragon.
The king said he could try but noted he had no armor, no horse, no sword.
Dratewka had only his shoemakers tools and a plan. He bought a dead sheep and some sulphur. Then he cut the sheep, stuffed it with the powdered sulphur. Then let them to a place where the dragon would see them.
The dragon comes out as expected, saw the sheep and greedily ate it.
The sulphur caught fire like a match and the dragon felt his stomach burning.
Dragon ran to the Vistula River and started drinking. Dragon drank and drank and couldn't stop... and the dragon burst.
At least people were free of him. The boy stays a hero.