Polish myths and legends

It would be cool to hear some famous polish myths and legends every country has them..
Would you like to share your favorite

For example about "Janosik", a man from the Polish Tatra mountains, who supposedly took the things from the rich and gave it away to the poor.

Is this similar to the "Robin Hood" legend?

Wikipedia has more information about this.

Slavic fairies
Siren
Syrenka

my favorite is Smok Wawelski's tale takes place in Kraków during the reign of King Krak, the city's legendary founder. Each day the evil dragon would beat a path of destruction across the countryside, killing the civilians, pillaging their homes and devouring their livestock. In many versions of this story, the dragon especially enjoyed eating young girls, and could only be appeased if the townfolk would leave a young girl in front of its cave once a month.

http://en.wikipedia.org/wiki/Smok_Wawelski

Yes Janosik is a Polish version of "Robin Hood" (even though he lived in a cave of the Tatra mountains, near Zakopane supposedly).

well as far as I know Mr Janosik was rather a Slovakian lad for some reason known as polish Robin Hood style hero.
being honest his nationality is bit a confusing
Have seen so called Janosik's cave somewhere near Liptovski Mikulash-Spisky Raj...

Thanks, Michal, fascinating!!!! and beautiful artwork!