Co Loa Citadel

More than 2,200 years ago, the ancient Viet people took up simple tools and set to work. They dug and piled up more than 2,200,000 cubic meters of earth. With it they raised three rings of earthen walls that spiral one inside another, about 16 kilometers long in all. Every bit of it was done by human strength and bronze tools.

This is Cổ Loa Citadel. And those earthen walls are still standing here, more than 2,000 years later.

Cổ Loa lies in the Đông Anh area of Hanoi, about 17 kilometers north of the city center. The name Cổ Loa is written in Chinese characters, and it means "old snail." The three rings of walls sit one inside the next, and seen from above they look like a giant snail shell.

That leaves the question of who built it.

According to a legend recorded in the Vietnamese histories, a chieftain named Thục Phán rose to power around the 3rd century BC. He defeated the eighteenth of the Hùng Kings, whom Vietnamese people honor as their ancestors. Then he took the throne under the name An Dương Vương and called his country Âu Lạc. The name joined two peoples, the Tây Âu and the Lạc Việt. He moved his capital from Phong Châu to Cổ Loa and ordered the citadel built.

For a long time, people suspected that this was only a legend. Then science had its say.

From 2005 to 2008, archaeologists from the University of Wisconsin-Madison in the United States worked with the Institute of Archaeology of Vietnam. Together they took soil samples from the walls of Cổ Loa and dated them by radiocarbon. The result showed that the citadel was built between the 3rd and the 2nd century BC. It matched the time of An Dương Vương in the legend.

Modern science has added evidence for what the Vietnamese histories recorded centuries ago.

The innermost ring, called Thành Nội, was the administrative center and the palace of An Dương Vương. It measures 1,650 meters around. The middle ring, Thành Trung, runs 6.5 kilometers around. The outermost ring, Thành Ngoại, runs 8 kilometers around. On average the walls stand 4 to 5 meters high, and in places they reach 12 meters, about as tall as a four-story building. At the base they are 20 to 30 meters wide.

If those 2,200,000 cubic meters of earth were shared evenly among 1 million people, each of them would have to dig and pile up more than 2 cubic meters. With bronze tools. With no machines.

And they did it.

Tens of thousands of three-edged bronze arrowheads have been found at Cổ Loa. Arrows of this kind had very good aerodynamics. They flew far and pierced armor well. They are physical evidence that Cổ Loa was a place where weapons were cast and stored. And perhaps the "magic crossbow" of folk memory was a crossbow that shot many arrows at once.

Those three-edged bronze arrowheads are also tied to the most tragic story of ancient Vietnam, the story of Mỵ Châu and Trọng Thuỷ.

According to the legend recorded in the histories, Triệu Đà was the king of Nam Việt, a land to the north. He attacked Âu Lạc many times, but each time the magic crossbow of An Dương Vương beat him back. So he pretended to make peace. He sent his son, Trọng Thuỷ, to Cổ Loa to marry into the royal family. The bride was Mỵ Châu, the daughter of the king. The young couple truly loved each other. But Trọng Thuỷ secretly swapped the trigger of the magic crossbow, then asked leave to go home and visit his father. Triệu Đà marched his army back, and this time the citadel fell.

An Dương Vương fled toward the sea with Mỵ Châu. She did not know that her husband was a spy. Along the road she kept scattering goose feathers, so that her husband could find her. But those very goose feathers showed the army of Triệu Đà the way.

When they reached the sea, Kim Quy, the Golden Turtle Spirit, appeared and spoke to An Dương Vương. "The enemy is sitting behind Your Majesty." Hearing this, An Dương Vương put his daughter to death right there on the shore, then went down into the sea. Trọng Thuỷ followed the trail of goose feathers, but he came too late. He brought his wife back to Cổ Loa to rest, and he too died beside the Ngọc Well.

Legend has it that the blood of Mỵ Châu flowed into the sea and turned into pearls. And washing those pearls in the water of the Ngọc Well made them shine brighter still.

The poet Tố Hữu folded that grief into two lines:

I tell the old story of Mỵ Châu. Her heart was set in the wrong place, up in her head.

The site still keeps the Thượng Temple, dedicated to An Dương Vương. It was built in 1687, under the Lê dynasty. The Ngọc Well sits in the middle of a pond. That is where, the legend says, Trọng Thuỷ died. The Mỵ Châu Shrine keeps a headless stone statue, the saddest image left from that story.

Those high earthen walls are still standing after more than 2,000 years. Before them, it is easy to see why people call this place the silent witness of a lost kingdom.

In 2012, the site was ranked a Special National Monument. But what stays longest is in the earthen walls themselves. Every layer of that earth holds the strength of the hands that dug it and piled it up, more than 2,200 years ago.