What are some top riddles?

One well-known riddle in Western literature is that of the sphinx: "What moves forward on four legs in the morning, two legs at noon and three legs at night?" The answer is man, who crawls in infancy, walks as an adult and uses a cane in old age.

J.R.R. Tolkien's character Gollum offers another famous riddle in "The Hobbit": "This thing all things devours / Birds, beasts, trees, flowers / Gnaws iron, bites steel / Grinds hard stones to meal / Slays king, ruins town / And beats mountain down." The answer to this riddle is time, which kills the living beings and materials mentioned through age and wear.