Egypt, Mesopotamia, and the Indus Valley were the three great civilizations of the Bronze Age. What made the Indus Valley Civilization distinct? Why did they decline? What is their legacy? In this lecture to his Chinese high school students, Jiang Xueqin explains that the Indus Valley Civilization (also known as the Harappan Civilization) was mainly a peaceful and egalitarian society, which prospered because of its global trade networks. This civilization had standardized weights and measurements, sophisticated urban planning, as well as private indoor latrines. The dramatic climate change of the 4.2 kiloyear event caused Egypt’s Old Kingdom, Mesopotamia’s Akkadian empire, and the Indus Valley Civilization to decline. The Egyptians left us the Pyramids, the Mesopotamians left us the Epic of Gilgamesh, and the Harappans left us spiritual wealth. From the interaction with the Proto-Indo-Iranians, the Harappan civilization would eventually give birth to Hinduism, Buddhism, Jainism, and Sikhism, which continue to give hope and meaning to billions of people today.