Gold Duck

Złota Kaczka is the heroine of a folk tale which has been recounted with many settings and by many writers, including the Young Poland poet Artur Oppman.
The story has come to be most closely associated with Warsaw, Poland.

Plot

In one version the Gold Duck, a princess who had been bewitched by an evil sorcerer, swam in a lake beneath Warsaw's Ostrogski Castle. She could be restored to human form only by someone who could spend 100 ducats a day over three consecutive days, without sharing this fortune with anyone.
A certain soldier was close to succeeding. But as the third day was drawing to a close, he gave the last grosz to a beggar, and the Gold Duck vanished together with the castle.