Medieval windmills dating from the 16th century on the hill of Campo de Criptana in Castilla La Mancha, Spain. In the novel, Don Quixote fights windmills that he imagines to be giants. Quixote sees the windmill blades as the giant's arms, for instance.
Tilting at windmills is an English idiom which means attacking imaginary enemies, or fighting unwinnable or futile battles. The word “tilt”, in this context, comes from jousting.
The phrase is sometimes used to describe confrontations where adversaries are incorrectly perceived, or courses of action that are based on misinterpreted or misapplied heroic, romantic, or idealistic justifications.