What are some of the oldest civilizations starting?


The oldest known urban civilization dates back 4000-3500 B.C and is known as Mesopotamia (meaning, between two rivers) which is modern day Iraq, Kuwait and Syria. Some of the Mesopotamian advancements includes Code of Hammurabi, Babylonian astronomy and the base 60 numeric system (that became the foundation of 60-second, 60 minute and 360-degree circle. 
Ancient Egyptian civilization(3100 BC) which was one of the most powerful empires that existed for almost 3000 years. It was based around the Nile river which today would extend from Syria to Sudan. Apart from the pyramids, they are famous for tombs, mummification and mausoleums. They also developed the 24-hour day along with 365 days calendar. The civilization ended around 332 B.C when Alexander the Great conquered it successfully. 
Around 2500 B.C., thrived the Indus valley civilization. The name comes from the Indus river valley that comprises modern day India, Pakistan and Afghanistan. It is deemed to be one of the most sophisticated civilization with organized city planning  with proper sewage and water supply systems. They were also extremely prolific inventors giving standardized weights and measures, metallurgy with copper, bronze, lead, and tin and seal carving. There is still debate among the historians and there are certain studies that suggests that Indus valley civilization might have pre-dated both ancient Egyptian and Mesopotamian. Irrespective, there is more unknown than known about this civilization. It is believed that climate change caused the decline of this extremely future forward civilization around 1700 B.C.