The Questioner of the Sphinx, 1863, oil on canvas by Elihu Vedder, 1836-1923, American symbolist painter, book illustrator and poet.
The Sphinx was thought to harbor the answers to great riddles. If the traveler knows the answer, he is permitted to pass into the area the Sphinx guards. Answer the riddle: There are two sisters, one gives birth to the other and she, in turn, gives birth to the first.