Do you know that large mounds sometimes have ancient cities hidden underneath them? In fact, the Indus Valley Civilization was discovered when an archaeologist, R.D. Bannerjee, visited Mohenjo-daro and saw a large mound. He thought there might be something underneath, and started digging. As the mud was gradually removed, an entire city was revealed!
How was this city covered with mud? When an ancient city began to decline, people left it, and moved elsewhere.
After hundreds of years, the abandoned buildings crumbled and broke down. The wind blew mud and sand over them, and when rain fell, the mud stuck to the buildings. In this way, the whole city was covered in mud, and as more and more mud and sand were deposited by the wind, a mound was formed. Harappa and the other cities of the Indus Valley Civilization were discovered when such mounds were excavated, or dug up.
Picture Credit : Google