The constellation Taurus is one of the oldest symbols. It's been associated with a bull even as far back as Babylonian times. In ancient Egypt, Taurus was associated with Apis, a bull-like incarnation of the god Osiris. In the Old Testament, Moses destroyed the Golden Calf. And in ancient Greece, Taurus commemorated the romance of Zeus and Europa--because Zeus transformed himself into a beautiful white bull to distract her, and carried her off to the island of Crete. Their son, Minos, became the king of Crete, and built a maze to hold another bull figure--the Minotaur, who was eventually killed by Theseus.
Aries is another constellation that has always been associated with a single image. Babylon, Egypt, Persia, Greece, and Rome, all of them considered Aries to be a ram. In Greece, Aries was most associated with Jason and the Argonauts, in the story of the quest for the Golden Fleece.
Jason was a victim of prophecy. Jason's father was killed by his brother Pelias. Jason was spirited away to protect him, but an oracle warned Pelias that the boy would return. Jason was raised by the centaur Chiron (who is represented by the constellation Sagittarius). When Jason challenged Pelias, the pretender told Jason he would give him the throne in return for the Golden Fleece.
Jason built a ship called the Argo, and crewed it with the Argonauts, some of the greatest heroes of Greece. Even Hercules sailed on the Argo. And with their help, he was finally successful.
Two of the Argonauts were named Castor and Pollux. They were twin sons of Zeus and Leda; one was immortal, the other was not. They were inseparable. At one point along the quest for the Fleece, Castor was killed, and immortal Pollux begged Zeus to let him die as well. Instead, Zeus placed them in the stars, side by side, never apart.