The major ancient civilization that developed along the Indus River is known as the Indus Valley Civilization, also referred to as the Harappan Civilization. Flourishing around 2500 BCE, it covered parts of modern-day Pakistan and northwest India. This civilization is noted for its advanced urban planning, including well-organized cities like Harappa and Mohenjo-Daro, sophisticated drainage systems, and a script that remains undeciphered. Their trade networks and agricultural practices demonstrate a high level of societal organization and cultural development, marking it as one of the world's earliest urban cultures.