Also known as Mesopotamia or Sumer, the cradle of civiliation

Agriculture
Writing, both pictograms and cuneiform
The wheel
Double-entry accounting and banking systems
The concept of privately owned property (vs. owned by the king)
King Hammurabi and first ever (known) set of written laws -- an important development, as it made it possible to have a rule of law, instead of just the whim of the ruler.
The Hanging Gardens of Babylon
Literature, incluing the Epic of Gilgamesh
Birthplace of Judaism (hence the term "semitic")

With the arrival of Islam and it's scholarly traditions, we can thank the entire Arab world for preserving the history and knowledge of ancient Egypt, Greece and Rome, particularly medicine and philosophy. Much of this work was done in Baghdad, one of the great cities of the Arab world. The scholars in Baghdad did not just preserve and translate the old works, but built upon it. Arab physicians were far more successful at not killing their patients than the European ones, and modern mathematics and algebra were invented.

Later European travellers brought this knowledge back to Italy, sparking the great Italian Renaissance by re-introducing knowledge that had been forgotten in Europe.