Final answer:
Harappa and Mohenjo-Daro were two main cities of the Indus Valley civilization, known for their advanced urban planning and organization.
Step-by-step explanation:
Harappa and Mohenjo-Daro were two main cities of the Indus Valley civilization. These cities emerged around 2800 BCE and were located in present-day Pakistan and India. They were highly organized and advanced, with sophisticated urban planning, drainage systems, and well-laid-out city streets. The Indus Valley civilization, including Harappa and Mohenjo-Daro, flourished from around 2600 to 1900 BCE.