In historical and fantastical drama, few tropes are as omnipresent as the Great Wall. The Great Wall divides civilizations. Often, inhabitants on one side of the wall wonder what wonders or horrors lie behind it, while stone-faced guards resolutely protect the wall against half-understood threats.

Of course, the most iconic example of the trope in fiction is Game of Thrones’s Wall, an enormous 800 foot tall ice structure that divides the Seven Kingdoms of Westeros from the wild men and ice zombies of the untamed northern wilderness. But walls that set a clear and discrete dividing line between two completely different worlds are everywhere in fiction, from Neil Gaiman’s Stardust to Rosemary Sutcliff’s Eagle of the Ninth. The problem with the trope, however, is that is caricatures the role walls actually played in historical civilizations. The reality is far more nuanced, and (if you ask me) far more interesting.

Obviously, the wall trope comes straight from history, with the Great Wall of China, Hadrian’s Wall, and the Berlin Wall all forming the template. Each of these historical structure are widely portrayed as a line marking the boundary between civilization and savagery, capitalism and communism, et cetera. I’m going to examine each of these famous walls and illustrate why they had little in common with the trope they inspired.

The Great Wall of China

Perhaps the most famous fortification in the entire world, the Great Wall of China stretches across thousands of miles of the northern Chinese frontier. Yet the wall was not one project. Various dynasties constructed many walls over a period of 2000 years, all of which are collectively considered the Great Wall.

The primary goal of the Great Walls (as it is more correct to call them) was to defend against the many Steppe nomads who frequently raided and invaded China. Yet the relationship between the Chinese on one side of the wall and the nomads on the other side is more complex than you might at first assume. For one thing, Chinese expeditions would frequently cross the Great Wall, either on military missions to fight with the nomadic tribes, or to trade with them. Furthermore, the borders were never so static as the walls imply. As Chinese dynasties and nomad empires rose and fell, the borders constantly shifted, and new walls were built.

Modern studies of steppe nomads (particularly by Owen Lattimore and Thomas Barfield) have revealed that nomadic societies depend on nearby sedentary people for weapons, luxury goods, and other things not available in a nomadic lifestyle. Similarly, the Chinese depended upon nomads to supply them with horses and skilled mercenaries. This symbiotic relationship ensured that steppe nomads never strayed far from Chinese towns, and each group depended upon the other. Mongolian historian Sechin Jagchid has even gone so far as to say that the nomads launched large-scale invasions of China only when China used its walls to shut off trade with them. From that perspective, walls were only a small (and occasionally counterproductive) part of Chinese strategy.

Few battles were actually fought on the walls, and when nomads did attack, they often broke through, most notably during the fall of the Song and Ming dynasties. By the time of the Qing dynasty (the final Chinese dynasty), the walls were used not to keep foreign invaders out, but to prevent Chinese workers from leaving and disrupting the economic basis for the nomad’s form of life. In short, the Great Wall as much a center for cultural mixing and economic control as it was a defensive fortification.

Hadrian’s Wall

Hadrian’s Wall (begun in 122 CE) is often viewed as the northernmost border of the Roman Empire, the line where all Roman power and civilization ended. It was the direct inspiration for the ancient, unconquerable wall that features in George R. R. Martin’s books. However, the truth is more complicated.

The border of the Roman Empire was far less rigid than people often assume. For starters, border fortifications moved a lot. Twenty years after construction began on Hadrian’s Wall, the Romans built the Antonine Wall, a different fortification about 100 miles north of Hadrian’s Wall. Some Roman forts went as far north as Perth and Dundee. Even after the Romans abandoned these northern fortifications and returned to Hadrian’s Wall, the frontier remained flexible.

Historian Adrian Goldsworthy has shown that often the frontier fortifications were very lightly garrisoned. In one survey of an 800 man cohort assigned to the northern fortifications, less than a third of the unit’s strength was actually deployed at the border. The majority of men were either escorting merchants, scouting beyond the walls, garrisoning towns behind the border, or similarly scattered. In many ways, the most important feature of Hadrian’s Wall was not the enormous ditches or impressive ramparts (neither of which were well maintained), but the regularly spaced gates, through which soldiers, merchants, and diplomats could (and very frequently did) travel. Indeed, for all of Roman history, aggressive raids into barbarian lands, to intervene in tribal politics and demonstrate Roman strength, was a vital part of Roman strategy.

It is also telling that walls built on the model of Hadrian’s were the exception in the Roman Empire. Whenever possible, the Romans preferred to set their frontiers at rivers (most notably the Rhine and Danube). This was only partly because of the defensiveness rivers offered. IT was also because rivers were the highways of the premodern world. Using rivers, the Romans could easily access huge swathes of land, transporting goods both to Roman settlements on the border and to “barbarians” on the opposite side. Had Britain contained any wide rivers stretching east to west, the Romans would likely have saved the effort of building walls and set up shop there instead.

In short, if you lived ten miles north of Hadrian’s Wall during the late Roman Empire, your life would probably have been very similar to that of your relatives living ten miles south of the wall. You would be closely monitored by the Roman legions, use goods from both sides of the wall, and could have passed through the wall with relative ease .

The Berlin Wall

Of all history’s famous walls, the one that most resembles the fiction trope is the Berlin Wall. If a person crossed the Berlin Wall, they would instantly be subject to completely different legal protocol, economic systems, and political governance. The five-yard journey across the wall could transform a person’s life, which is why so many people tried desperately to cross. Yet the Berlin Wall is also the least applicable to the scenarios typically present in fiction.

The Berlin Wall did not serve a military purpose, which distinguishes it from most other walls, both in fiction and history. Instead, it existed solely to control population flow. The Berlin Wall in many ways an artificial wall, more symbolic than impactful. The differences between West Berlin and East Berlin had nothing to do with the wall, but were instead the products of treaties and diplomacy. The wall merely formalized what already existed, rather than allowing it to exist in the first place.

Modern walls, from the Berlin Wall to the partially-complete wall on the US-Mexico border, are symbols of legal change, rather than defensive or military constructions. Yet even these modern fortified borders, though much is made of their impassability, see thousands of people pass through them, both legally and illegally. The hundreds of people who crossed the Berlin Wall each day to go to work would have seen the construction not as the mystical barrier out of fantasy tropes, but as a mundane and temporary inconvenience to their everyday lives.

Points of Contact, Not Exclusion

Fiction likes to portray big fortifications as permanent, defensive, and impenetrable on both sides. Yet historically, repelling people has been only a small part of the roles walls play in empires. No wall can repel everyone, and even if they could, what’s the point to building a wall that you yourself cannot pass through? Most of the time, people moved regularly through the great walls of history.

In fact, walls may increase a land’s connectivity with the “outside.” After all, the enormous effort that goes into building and garrisoning walls means that a large population must remain permanently in close proximity with the outside. Given the permeability of walls, these people will inevitably come in contact with foreign goods and customs, and bring them back into the heartland. Far from being the ultimate symbol of exclusion, walls often enmesh previously distinct societies.