The geography of Mesopotamia, encompassing its ethnology and history, centered on the two great rivers, the Tigris and Euphrates.
Mesopotamia was a historical region situated within the Tigris–Euphrates river system, in modern days roughly corresponding to most of Iraq plus Kuwait, the eastern parts of Syria, Southeastern Turkey, and regions along the Turkish-Syrian and Iran–Iraq borders.
Ethnology is the branch of anthropology that compares and analyzes the characteristics of different peoples and the relationships between them.
The Tigris is the eastern member of the two great rivers that define Mesopotamia, the other being the Euphrates.
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While the southern is flat and marshy, the near approach of the two rivers to one another, at a spot where the undulating plateau of the north sinks suddenly into the Babylonian alluvium, tends to separate them still more completely.
Alluvium is loose, unconsolidated soil or sediment that has been eroded, reshaped by water in some form, and redeposited in a non-marine setting.
Babylon was a key kingdom in ancient Mesopotamia from the 18th to 6th centuries BC.
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In the earliest recorded times, the northern portion was included in Mesopotamia; it was marked off as Assyria after the rise of the Assyrian monarchy.
Assyria was a major Mesopotamian East Semitic-speaking kingdom and empire of the ancient Near East.
Apart from Assur, the original capital of Assyria, the chief cities of the country, Nineveh, Kalaḫ and Arbela, were all on the east bank of the Tigris.
Aššur, also known as Ashur and Qal'at Sherqat, was the capital of the Old Assyrian Empire, the Middle Assyrian Empire, and for a time, of the Neo-Assyrian Empire.
Nineveh was an ancient Assyrian city of Upper Mesopotamia, located on the outskirts of Mosul in modern-day northern Iraq.
The reason was its abundant supply of water, whereas the great plain on the western side had to depend on streams flowing into the Euphrates.