Collection of facts about Sumer

This post is a collection of facts about Sumer (c. 5500 - 1800 BC). There are 7 facts listed below. Source: Wikipedia

• World's earliest known civilization
• Located along Tigris and Euphrates rivers
• Ubaid period (c. 6500 - 4100 BC)
• Uruk period (c. 4100 - 3100 BC)
• Proto-writing (c. 4000 - 2500 BC)
• World's earliest known texts (27th century BC)
• Succeeded by Akkadian Empire (23rd century BC)