During the Classical Era, early civilizations expanded beyond river valleys and developed systems of thought, culture, art, music, and literature that still influence us today. These civilizations began reflecting on morality and the meaning of life, giving rise to the world's major religions. As Persia, Greece, Rome, India and China advanced, they established classical standards in many areas that works were judged against for over 2,000 years, earning them the name "classical civilizations."