A Centuries-Old Mystery: Did This Elusive Viking City Exist?

After the local government decided to build an observation tower atop a sandy hill on Wolin, an island in the Baltic Sea, a Polish archaeologist was called in to check the site before construction and look for buried artifacts from the spot’s macabre past.

Hangmen’s Hill, a public park, had in earlier times been an execution ground, a cemetery and, some believe, a place for human sacrifices — so who knew what grisly discoveries were in store?

But what the archaeologist, Wojciech Filipowiak, found when he started digging caused more excitement than distaste: charcoaled wood indicating the remains of a 10th-century stronghold that could help solve one of the great riddles of the Viking Age.

Was a fearsome fortress mentioned in ancient texts a literary fantasy or a historical reality?

It has long been known that Nordic warriors established outposts more than a millennium ago on Poland’s Baltic coast, enslaving indigenous Slavic peoples to supply a booming slave trade, as well trading in salt, amber and other commodities.

Not known, however, was the location of the Vikings’ biggest settlement in the area, a town and military stronghold that early 12th-century texts called Jomsborg and linked to a possibly mythical mercenary order known as Jomsvikings.

Some modern scholars believe that Jomsborg was never a real place, but instead a legend handed down and embroidered through the ages. The findings at Hangmen’s Hill on Wolin Island might alter that view.

“It is very exciting,” said Dr. Filipowiak, a scholar in Wolin with the archaeology and ethnology section of Poland’s Academy of Sciences. “It could solve a mystery going back more than 500 years: Where is Jomsborg?”

Interest in Vikings, once largely confined to a niche field of academic study, has surged in recent years as television series like “Game of Thrones,” movies, graphic novels and video games have embraced — and distorted — Norse themes, clothing and symbols. The Viking Age, or at least a rough approximation of it, has become a fixture of popular culture.

This has been good news for the tourism business in Wolin. “Vikings are sexy and attract a lot of interest,” said Ewa Grzybowska, the mayor of Wolin, which includes a town and a wider island district with same name.

But the mayor bemoaned that far fewer visitors come to her domain than to a nearby beach resort. She said more money was needed to carry out excavation work and develop Wolin as a world-class destination for Viking researchers and amateur enthusiasts.

Pointing out of her window in City Hall to a square that is believed to contain a treasure of unexcavated early medieval artifacts, she said: “Wherever you go here, there is a piece of history.”

That history, however, has often been a source of discord.

Nazi archaeologists scoured Wolin, which was part of Germany until 1945, for evidence of the presence of Vikings — and for proof of what the Nazis believed was the superiority of the Nordic race and its dominance in the early medieval period over local Slavic peoples, who later came to identify themselves as Poles and claimed the land for Poland.

When Poland took control of Wolin after World War II, Polish archaeologists hunted for artifacts that would enhance their country’s hold on former German lands and help reinforce a sense of national identity.

Schools in Wolin organized re-enactments of Viking invasions of Poland’s Baltic coast and, for decades after World War II, “far more kids wanted to be Slavs defending the island,” said Karolina Kokora, director of Wolin’s history museum.

That changed after Poland ditched communism and began turning West, away from Russia and its emphasis on Slavic pride. “After 1989, everyone wanted to be a Viking,” Ms. Kokora recalled.

Public fascination with Vikings has also led to a surge in historical sleuthing by amateurs.

Among them is Marek Kryda, a Polish American amateur historian and author of a polemical 2019 book that denounced Polish archaeology as a morass of ethnic chauvinism mostly blind to the role Vikings played in the early formation of Poland.

Mr. Kryda set off a storm of controversy last summer in Poland after he announced in The Daily Mail, a British tabloid, that he had located the likely grave of Harald Bluetooth, the historical Danish Viking king who once ruled in this area.

The consensus view among historians is that Harald probably died in the region at the end of the 10th century but had been buried in Denmark.

Mr. Marek said he had placed Harald’s likely burial mound in Wiejkowo, a tiny village inland from Wolin, by using satellite imaging. Dr. Filipowiak dismissed that as “pseudoscience.”

The furor over where Harald Bluetooth is buried has turned the Viking king — celebrated as a unifier of feuding Nordic fiefs and the inspiration for the name of a wireless technology designed to unite devices — into an agent of noisy division.

Ms. Grzybowska, the mayor, said she was not qualified to judge whether Harald was buried in her district but added that she would be delighted if true. “It would add special splendor and grandeur to our island,” she said.

Ms. Grzybowska’s district has a Slavs and Viking Village, dotted with thatched wooden huts and a stone inscribed with runes celebrating Harald Bluetooth. But these are modern fakes — representations of a distant Viking past that excites the imagination but has been hard to pin down with certainty despite the decades of digging by archaeologists looking for traces of Jomsborg.

Ms. Kokora, the museum director, described the elusive 10th-century settlement as a “medieval New York on the Baltic” — a trading entrepôt with a mixed population of Vikings, Germanic people and Slavs — that had mysteriously vanished from the map, leaving only whiffs of its existence in archaic texts.

It is said to have had thousands of inhabitants, a fortress and a long pier to accommodate the Viking ships that sailed to and from Scandinavia and as far as North America. Traces of enslaved Slavs traded along the Baltic coast in the first millennium have been found thousands of miles away in Morocco.

Sifting through shards of excavated pottery on a cluttered table in her museum, Ms. Kokora said the Vikings hadn’t bothered much with making pots and were not very good at it. “They just took from the Slavs,” she said.

In the 1930s, German archaeologists, eager to challenge Polish claims that the area had originally been settled mainly by Slavs, excavated a mound on the opposite side of town from Hangmen’s Hill in the hope of finding traces of Jomsborg — and proof that Scandinavians, an important pillar of the Nazi ideology of Aryan supremacy, had been there first. They found some artifacts but no evidence of a Viking stronghold.

Parts of Hangmen’s Hill had been excavated before Dr. Filipowiak started digging, but not the area selected for construction. The archaeologist said his serendipitous find of what he thinks could be the ramparts of 10th-century Jomsborg’s stronghold still needed more analysis, but he believes there is already “80 percent certainty” that this is the site.

The debate over Jomsborg’s location — or if it really existed — has been “a very long discussion,” Dr. Filipowiak said. “Hopefully, I can help end it.”