Great Wall of Gorgan

Look down at the ground near your feet. The earth here has a faint reddish tint, and in places you may spot small chips of baked brick scattered through the soil. They look like nothing much. Yet each fragment is a piece of one of the largest building projects of the ancient world. The wind moves across open farmland, and the long, low ridge in front of you runs on toward the horizon... and keeps going.

This is the Great Wall of Gorgan, in Golestan Province in northeastern Iran. Local people have long called it the Red Snake, or Qizil Alan in the Turkmen language. The name comes from the colour of its fired bricks, and from the way it winds across the plain. For centuries, few outsiders paid it much attention. Today, many archaeologists count it among the most important frontier walls ever built.

The scale is hard to picture from one spot. The wall stretches for roughly two hundred kilometres. It begins near the shore of the Caspian Sea in the west. From there it crosses the Gorgan Plain and reaches the foothills of the mountains in the east. That makes it longer than Hadrian's Wall and the Antonine Wall in Britain combined. Standing here, you see only a tiny slice of the whole line.

For a long time, nobody agreed on who built it. Local tradition linked it to Alexander the Great, and some called it Alexander's Barrier. Other scholars suggested the Parthians, an Iranian dynasty that ruled before the Sasanians. Some credited a famous Sasanian king of the sixth century. Each idea had supporters. None had firm proof. The wall kept its secret through most of the twentieth century.

The answer came from careful science, not legend. In the early 2000s, a joint team of Iranian and British archaeologists began new excavations here. They collected charcoal from the brick kilns and tested it with radiocarbon dating. They also used a method that measures when buried sediment last saw sunlight. The results pointed clearly to the Sasanian Empire, most likely the fifth century. The Sasanians were the last great Persian dynasty before the arrival of Islam.

Here is a detail that most visitors miss. The builders did not simply pile up earth and stone. They dug a canal along the line of the wall. This canal carried water across a dry landscape. The workers needed that water to make bricks, and they made them in huge numbers. Archaeologists have found the remains of many kilns along the route. Each kiln baked mud into the hard red bricks that gave the Red Snake its colour.

The bricks themselves are worth imagining. Most were large, flat squares, heavier than a modern house brick. Millions of them went into the wall. Workers laid them in mortar to create a solid barrier, with a deep ditch running in front on the northern side. The ditch made any attack slower and more dangerous. Today, the ditch has mostly filled with soil, but in some places you can still trace a gentle hollow beside the ridge.

A wall alone cannot defend a frontier. Soldiers must live along it. Researchers have identified more than thirty forts attached to the line, spaced at intervals along its length. Many of them were large and rectangular. From the air, their outlines still show as square mounds in the fields. Archaeologists have suggested that a very large army may have been stationed here at its height. If so, this was not a quiet border. It was a heavily guarded front line.

So what were they guarding against? The wall faces north, toward the steppe. Beyond lay the lands of nomadic peoples who moved with their herds across Central Asia. Many historians believe the main threat was the Hephthalites, sometimes called the White Huns. They were a powerful group who fought the Sasanians more than once. The wall, the forts and the canal show how seriously the empire took that danger.

Now consider a second surprise. The Gorgan wall was only part of a wider system. To the southwest, another barrier known as the Tammisheh Wall ran from the mountains toward the sea. Together, these defences closed off the narrow gap between the Caspian and the Alborz Mountains. Armies coming from the north had to pass through this corridor. The Sasanians decided to control it with brick, water and men.

Time has been hard on the Red Snake. After the empire fell, people took bricks from the ruins for their own homes and farms. Rain, ploughing, roads and railways have cut through the line in many places. What you see today is mostly a low, softened mound, often covered in grass or crops. It does not tower over you like the walls of China. Its power is in its length and its quiet persistence.

Take a moment to look around at the landscape. This is the Gorgan Plain, an open, fertile country of wheat fields, cotton and grazing land. Turkmen communities have lived in this region for generations, and you may see their villages and livestock nearby. The nearby town of Gonbad-e Kavus has its own famous medieval brick tower. Brick, it seems, has shaped this region for a very long time.

Before you leave, look once more along the ridge. Follow it with your eye until it fades into the fields. Somewhere out there, it continues toward the sea on one side and the mountains on the other. The soldiers, the brickmakers and the canal diggers are long gone. But the red earth under your shoes is still their work. As you walk back, watch the ground. You may find that the wall is everywhere around you.