Apollo (əpŏl´ō), in Greek religion and mythology, one of the most important Olympian gods, concerned especially with prophecy, medicine, music and poetry, archery, and various bucolic arts, particularly the care of flocks and herds. He was also frequently associated with the higher developments of civilization, such as law, philosophy, and the arts. As patron of music and poetry he was often connected with the Muses. Apollo may have been first worshiped by primitive shepherds as a god of pastures and flocks, but it was as a god of light, Phoebus or Phoebus Apollo, that he was most widely known. After the 5th cent. BC he was frequently identified with Helios, the sun god. Apollo was the father of Aristaeus, Asclepius, and, in some legends, Orpheus, although his amorous affairs were not particularly successful. Daphne turned into a laurel rather than submit to him, and Marpessa refused him in favor of a mortal. He gave Cassandra the gift of prophecy, and when she disappointed him, he decreed that no one would believe her prophecies. His chief oracular shrine was at Delphi, which he was said to have seized, while still an infant, by killing its guardian, the serpent Python. This event was celebrated every eight years in the festival of the Stepteria. Other festivals held in Apollo's honor included the yearly Thargelia, to celebrate spring, and the Pythia, held every four years to honor his victory over the Python. Besides Delphi, his other notable shrines were at Branchidae, Claros, Patara, and on the island of Delos, where, it was said, he and his twin sister, Artemis, were born to Leto and Zeus. In Roman religion, Apollo was worshiped in various forms, most significantly as a god of healing and of prophecy. In art he was portrayed as the perfection of youth and beauty. The most celebrated statue of him is the Apollo Belvedere, a marble statue in the Belvedere of the Vatican.