If you’ve ever voted, served on a jury, watched a movie, read a novel, spoken English, had a rational thought, or gazed at the night sky in silent wonder, then you can thank the Ancient Greeks. They brought us democracy, science, philosophy, written contracts, taxes, writing, and schools. But the apex of their civilization, sandwiched between two wars, lasted just 24 years—in human history, a lightning flash across the summer sky.

For much of its history, Athens was either preparing for war, at war, or recovering from war. But in the window between the Persian and Peloponnesian Wars, from 454 to 430 B.C., the city was at peace, and it flourished. The Athenians were “not very numerous, not very powerful, not very organized,” as the classicist Humphrey Kito noted, but they nevertheless “had a totally new conception of what human life was for, and showed for the first time what the human mind was for.”

Like Silicon Valley today, ancient Athens during this brief period became a talent magnet, attracting smart, ambitious people. A city with a population equivalent to that of Wichita, Kansas, it was an unlikely candidate for greatness: Other Greek city-states were larger (Syracuse) or wealthier (Corinth) or mightier (Sparta). Yet Athens produced more brilliant minds—from Socrates to Aristotle—than any other place the world has seen before or since. Only Renaissance Florence came close.

One of the biggest misperceptions about places of genius, though, is that they are akin to paradise. To the contrary, ancient Athens was a place of public opulence and private squalor. The streets were noisy, narrow, and dirty. The houses of the wealthy were indistinguishable from those of the poor, and both were equally shoddy—constructed of wood and sun-dried clay, and so flimsy that robbers gained entry by simply digging.

How did a small, dirty, crowded city, surrounded by enemies and swathed in olive oil, manage to change the world? Was Athenian genius simply the convergence of “a happy set of circumstances,” as the historian Peter Watson has put it, or did the Athenians make their luck? This question has stumped historians and archaeologists for centuries, but the answer may lie in what we already know about life in Athens back in the day.

The ancient Athenians enjoyed a deeply intimate relationship with their city. Civic life was not optional, and the Athenians had a word for those who refused to participate in public affairs: idiotes. There was no such thing as an aloof, apathetic Athenian. “The man who took no interest in the affairs of state was not a man who minded his own business,” wrote the ancient historian Thucydides, “but a man who had no business being in Athens at all.” When it came to public projects, the Athenians spent lavishly. (And, if they could help it, with other people’s money—they paid for the construction of the Parthenon, among other things, with funds from the Delian League, an alliance of several Greek city-states formed to fend off the Persians.)

All of ancient Athens displayed a combination of the linear and the bent, the orderly and the chaotic. The Parthenon, perhaps the most famous structure of the ancient world, looks like the epitome of linear thinking, rational thought frozen in stone, but this is an illusion: The building has not a single straight line. Each column bends slightly this way or that. Within the city walls, you’d find both a clear-cut legal code and a frenzied marketplace, ruler-straight statues and streets that follow no discernible order.

In retrospect, many aspects of Athenian life—including the layout and character of the city itself—were conducive to creative thinking. The ancient Greeks did everything outdoors. A house was less a home than a dormitory, a place where most people spent fewer than 30 waking minutes each day. The rest of the time was spent in the marketplace, or working out at the gymnasium or the wrestling grounds, or perhaps strolling along the rolling hills that surround the city. Unlike today, the Greeks didn’t differentiate between physical and mental activity; Plato’s famous Academy, the progenitor of the modern university, was as much an athletic facility as an intellectual one. The Greeks viewed body and mind as two inseparable parts of a whole: A fit mind not attached to a fit body rendered both incomplete.

And in their efforts to nourish their minds, the Athenians built the world’s first global city. Master shipbuilders and sailors, they journeyed to Egypt, Mesopotamia, and beyond, bringing back the alphabet from the Phoenicians, medicine and sculpture from the Egyptians, mathematics from the Babylonians, literature from the Sumerians. The Athenians felt no shame in their intellectual pilfering. Of course, they took those borrowed ideas and put their own stamp on them—or, as Plato put it (with more than a touch of hubris): “What the Greeks borrow from foreigners, they perfect.”

Athens also welcomed foreigners themselves. They lived in profoundly insecure times, but rather than walling themselves off from the outside world like the Spartans, the Athenians allowed outsiders to roam the city freely even during wartime, often to the city’s benefit. (Some of the best-known sophists, for example, were foreign-born.)

It was part of what made Athens Athens—openness to foreign goods, new ideas, and, perhaps most importantly, odd people and strange ideas.

The city had more than its fair share of prominent homegrown eccentrics. Hippodamus, the father of urban planning, was known for his long hair, expensive jewelry, and cheap clothing, which he never changed, winter or summer. Athenians mocked Hippodamus for his eccentricities, yet they still assigned him the vital job of building their port city, Piraeus. The writer Diogenes, who regularly ridiculed the famous and powerful, lived in a wine barrel; the philosopher Cratylus, determined never to contradict himself, communicated only through simple gestures.

Then there was that greatest of Athenian oddballs, Socrates. Never before or since have a man and a city been so perfectly matched. Eccentric, barefoot, and stubborn, Socrates occupied that precarious position that all geniuses do, perched between insider and outsider. He was far enough from the mainstream to see the world through fresh eyes, yet close enough to it that his insights resonated. Socrates loved Athens and would never consider living—or dying—anywhere else. After being charged with impiety and “corrupting the youth,” he was given the choice between leaving Athens and execution. He chose the latter.

Socrates is remembered as a great philosopher, but he was first and foremost a conversationalist, pioneering conversation as a means of intellectual exploration. One of his favorite pastimes, like many Athenians, was the symposium—literally “to drink together”—where entertainment, according to the historian Robert Flacelière, consisted of “anything from good talk and intellectual puzzle games to music, dancing girls, and similar titillations.” At these gatherings, food was served, but that was almost beside the point. The Athenians were not foodies—most people, no matter their social stature, were satisfied with a hunk of bread, onions, and a small handful of olives. Overall, their caloric intake was remarkably low. Aristophanes, the satirist, credited the meager Athenian diet with keeping their bodies lean and their minds sharp.

And of course, no symposium was complete without wine, and lots of it. While the ancient Greeks enthusiastically endorsed moderation, they seldom practiced it. Moderation was considered an end, not a means; go to enough extremes, they figured, and eventually they cancel each other out. They were adventurous beyond their power, and daring beyond their judgment,” as Thucydides put it, and equally extreme in their enthusiasm for their home. Consider this swagger from the comic poet Lysippus: “If you haven’t seen Athens, you’re a fool; if you have seen it and are not struck by it, you’re an ass; if you are pleased to go away, you’re a packhorse.”

Perhaps every place of genius is equally overzealous. Perhaps that is why they never last long.

In 1944, an anthropologist named Alfred Kroeber theorized that culture, not genetics, explained genius clusters like Athens. He also theorized why these golden ages invariably fizzle. Every culture, he said, is like a chef in the kitchen. The more ingredients at her disposal (“cultural configurations” he called them), the greater the number of possible dishes she can whip up. Eventually, though, even the best-stocked kitchen runs dry. That is what happened to Athens. By the time of Socrates’s execution, in 399 B.C., the city’s cupboard was bare. Its “cultural configurations” had been exhausted; all it could do now was plagiarize itself.

The Athenians also hastened their demise by succumbing to what one historian calls “a creeping vanity.” Eventually, they reversed their open-door policy and shunned foreigners. Houses grew larger and more ostentatious. Streets grew wider, the city less intimate. People developed gourmet taste. The gap between rich and poor, citizen and noncitizen, grew wider, while the sophists, hawking their verbal acrobatics, grew more influential. Academics became less about pursuing truth and more about parsing it. The once vibrant urban life degenerated.

While they didn’t know that their time in the sun would be so brief, the Athenians did know, as their famed historian Herodotus once noted, that “human happiness never remains long in the same place.” Neither, it seems, does genius.

This article has been adapted from Eric Weiner’s book, The Geography of Genius: A Search for the World's Most Creative Places, from Ancient Athens to Silicon Valley.