The source of Mesopotamia civilization can be found in the NCERT Solutions - Writing and City Life History, Class 11, World History. Mesopotamia, which means "land between rivers" in Greek, was located in the eastern part of the Fertile Crescent, between the Tigris and Euphrates rivers in modern-day Iraq. It was one of the earliest civilizations in the world, flourishing from around 3500 BCE to 500 BCE.

The NCERT Solutions - Writing and City Life History, Class 11, World History provides a detailed account of the sources that contribute to our understanding of Mesopotamian civilization. These sources include:

1. Cuneiform Writing: Mesopotamia is known for its invention of writing, specifically the cuneiform script. Cuneiform tablets have been discovered, containing various texts such as administrative records, legal codes, religious hymns, and literary works. These writings provide valuable insights into the social, political, economic, and religious aspects of Mesopotamian society.

2. Archaeological Discoveries: Excavations in Mesopotamia have unearthed numerous artifacts, structures, and ancient cities. These archaeological findings help reconstruct the material culture of the civilization, including pottery, tools, weapons, jewelry, and monumental architecture. The ruins of cities like Ur, Uruk, and Babylon offer glimpses into the urban planning, architecture, and city life of ancient Mesopotamia.

3. Historical Accounts: Mesopotamia is mentioned in various historical accounts from neighboring civilizations, such as Egypt and Greece. For example, the famous Greek historian Herodotus wrote about the conquests of the Persian Empire, which included Mesopotamia. These accounts provide external perspectives on the political and military history of the region.

4. Epics and Mythology: Mesopotamian literature, particularly the Epic of Gilgamesh, offers insights into the religious beliefs, values, and mythological stories of the civilization. The epic narrates the adventures of Gilgamesh, a legendary king, and explores themes of mortality, friendship, and the relationship between gods and humans.

In conclusion, the NCERT Solutions - Writing and City Life History, Class 11, World History is a reliable source for understanding the civilization of Mesopotamia. It covers the various sources that contribute to our knowledge of this ancient civilization, including cuneiform writing, archaeological discoveries, historical accounts, and literary works. By studying these sources, we can gain a comprehensive understanding of the rich history and culture of Mesopotamia.