Mesopotamia (Uruk · Ur · Nippur)
Where civilization first wrote itself down.
Kernel
Mesopotamia is the place where the operating system of civilization was first booted. Cuneiform, the wheel, irrigation arithmetic, base-60 time-keeping, the legal code, the city wall, the temple-as-bureaucracy — almost every primitive that later civilizations reorganized around began on the alluvial flatland between the Tigris and Euphrates. The first technological center was not a city; it was a way of recording that a city had happened.
Why it rose
Two rivers, one floodplain, and a calendar. The Tigris and Euphrates flooded predictably enough that agriculture could be planned, but unpredictably enough that planning required institutions. Surplus grain financed temples; temples invented accounting; accounting invented writing. By 3100 BCE Uruk had a population of ~40,000 — perhaps the densest human concentration that had ever existed — and a clerical class running a redistribution economy on clay tablets.
What it gave the world
Writing, in the sense we still use the word. Number, in the abstract. Law, in the sense that a statute outlasts the king who issued it. Astronomy as a state function — Babylonian sky-tablets enable Greek mathematics two millennia later. The base-60 system survives in our minutes, our hours, our 360° circles. The very metaphor of "running" a city as a system is Mesopotamian.
Why it declined
Salinization of irrigated fields slowly destroyed productivity; military pressure from highland and steppe peoples (Akkadians, Amorites, Kassites, eventually Assyrians and Persians) recomposed the political layer faster than the institutional layer could adapt. By the time Babylon fell to Cyrus in 539 BCE the cultural substrate had migrated west to Greek-speaking thinkers and east toward Persia. Knowledge stayed; centers moved.