The Harappan civilization existed along the Indus River in modern-day Pakistan from around 4000-1000 BC. The cities of Harappa and Mohenjo-Daro were centers of this civilization and had advanced town planning with organized streets and drainage systems. Houses were built with baked bricks and arranged around a central courtyard, while public buildings included granaries and wells. The Indus Valley provided fertile land for agriculture and protection from the Himalayas, contributing to the success of the Harappan civilization.