Sumeria, the great-great-great-grandfather of all civilizations. Sorta. Well, from the American point of view, Sumeria is kind of like the REALLY old guy in your family reunion who you are barely related to and can't remember the name of.
There were a group of people living in the southern part of the Arabian peninsula. At some point they decided that living in the desert totally sucked and they wanted to move north. A few centuries later, they found themselves in Mesopotamia (they walked really slowly). There they decided that living in a place with food and water was a little better than their previous choice of residence.
After a while, they had built themselves some nice cities. They called the area they lived in "Sumer". Then they called themselves Sumerians, to identify themselves as different from all the other people who were living in the area. Then they came up with a revolutionary new idea: Math. They made a base math system that we still use (in part) today.
What was this new system you ask? Sixty. The number 60 was the base for all math. Sixty as a base? Can you think of anything we use that's like that? I'll give you a "hint":
Yes, the Sumerians came up with our system of telling time. A system that is now about 5,000 years old. Go Sumeria!
But wait, there's more! The Sumerians also came up with geometry. They invented the "degree" system of measuring circles which we still use today! Notice that 360 can be divided by 60 quite nicely into, you guessed it, 6.
Anyway, the Sumerians were then officially the first civilization to ever grace the planet's surface. Since they were pretty much the rulers of the world (at least, their world), and they knew it, they decided to try and make a base religion too. This failed miserably. Why? Because the Sumerians had a god for just about everything. And I mean everything.
They had so many gods that if you could memorize enough names and mythology, you became a priest. And the priests basically ran everything except the army. That was the job of the local general.
So their religion didn't really catch on, but who cares? They were the only civilization on the planet, they were protected from almost all harm by default... right? As it turns out, the Sumerians were undone by none other than... the Sumerians! Yes, civil wars against rivaling cities brought the Sumerian chapter of history nearly to an end.
Then the babylonians came.
Then that chapter of history was closed with such force that it knocked the rest of the Middle East off of its feet, which the Babylonians promptly chopped off.