The Turkish people have been used to the sight of Scandinavians descending on their coastal regions for more than a millennium. 

Long before package holidays were invented, Vikings first raided, then traded, and became such an intrinsic part of the then Byzantine Empire that they were entrusted to be the personal bodyguard of the emperor

The work of angels, not human beings

When it was completed in the space of a mere five years, it had no peer in Christendom. 

The two architects of the church, Anthemius of Tralles and Isodorus of Miletus, had created, according to one contemporary poet, "a dome that vies in rank with the nine spheres of heaven!"

The cost was so astronomical that it amounted to a fifth of the total annual revenue for one of the largest empires in history. 

Later, when one 19th-century Italian traveler saw it, he wrote that "it is an architectural looks like the work of angels, not of human beings." 

It has become the symbol of two empires, two religions, and one modern nation-state.

We are, of course, talking about the heavenly Hagia Sophia (Greek for "Holy Wisdom"), the 6th-century church located in what is now Istanbul but was, until 1930, the ancient city of Constantinople. 

Commissioned by Byzantine Emperor Justinian I, it was completed at a breakneck speed in 537 CE and was considered an architectural marvel well into the modern period. 

A towering church, it dominates the skyline of this ancient city, situated on the Bosphorus, the very meeting point of two continents, Europe and Asia.

Those that have wandered inside this now-working mosque and looked upward saw its piece de la resistance – a massive dome, some 31 meters / 101 feet wide and 56 meters / 184 feet high – which seems to be suspended mid-air. 

This type and scale of construction would not be attempted again until its successor for Christianity, St. Peter's Basicilia in Rome, was completed more than a millennium later!

The Hagia Sophia in Istanbul is widely seen as a symbol of consistency, enduring through different time periods. Photo: Boris Stroujko / Shutterstock

Overseen a constant flow of peoples, cultures, and civilizations

If there is one constant in Istanbul, it is the Hagia Sophia. It has seen every empire, every civilization, and everyone come and go: the Romans, the Byzantines, the Crusaders, the Seljuks, the Ottomans, and now the modern İstanbullu (Istanbulites).

A Christian church for almost the first millennium of its life, it was first a symbol of the might of then Roman Empire. 

When the Western part of the Roman Empire disintegrated during the 5th century CE, the Eastern portion, of which Constantinople was its capital, survived and evolved into what later historians have somewhat confusingly called the "Byzantine Empire."

For the next half a millennium, the Hagia Sophia would become the symbol of a strong branch of highly orthodox Christianity, sending missionaries all over the early medieval world, including as far away as the Kievan Rus (encompassing a huge swathe of northeastern Europe). 

This huge empire was not only founded by Viking warriors, pushing eastward from Scandinavia from the late 8th century CE but also is seen as the ancestor of the modern nations of Belarus, Russia, and Ukraine.

Yet this was not the only place where these two different cultures met.

Viking warriors and merchants, who often went hand in hand with each other during the "Viking expansion" (during the first half of the 9th century CE), traveled and traversed the many river systems of Eastern Europe and would eventually arrive in Constantinople, so impressive to the Viking eye it was labeled Miklagard (Old Norse for "The Great City").

Aside from becoming just another series of peoples selling their wares (including humans) on the streets of Constantinople, Viking warriors were so prized that they became the foundation of an elite personal bodyguard for the Byzantine Emperor himself, the Varangian Guard from 988 CE. 

The most famous commander of this guard was Harald Hardrada, perhaps the epitome of a Viking warrior king, whose failed usurpation of the English crown, on a battlefield in northern England in 1066 CE, often overshadows his military prowess throughout a long and storied career.

So when runic inscriptions were discovered, etched on the walls of the Hagia Sophia, this was just further proof not only of the longevity of the mosque but also of the cultural and civilizational melting pot Constantinople once was. 

However, this graffiti was unlike others found as it was in the form of runic inscriptions, the alphabet of people from Viking societies. The mystery of these inscriptions, what they said, and who inscribed them has only recently been unlocked.

According to Selçuk Eracun, the Hagia Sophia Viking inscription states, "Halfdan was here." Photo: Dreamer Company / Shutterstock

Halfdan was here

For many years, Selçuk Eracun, was the face of the Hagia Sophia for hordes of tourists visiting every year. 

As well as being a professional tour guide, Eracun is also a researcher and writer who has spent more than 25 years showing the world the beauty of the Hagia Sophia. 

Speaking to the Daily Sabah, Eracun spoke of how the runic inscriptions, since their discovery in the 1970s, had become an area of intense interest for scholars and researchers.

It was Eracun himself who deciphered the inscription, discovering the sentence "Halfdan was here." 

Given that Viking people used a runic alphabet and Halfdan is very much a Viking name, we can safely assume that a Viking etched this graffiti on the walls of the Hagia Sophia. 

However, Eracun, points to further proof that this person was indeed a Viking. During his research, he also discovered that this 1-meter / 3-foot-long inscription also featured a Viking ship.

Following decades of further detailed research, Eracun postulated that this Halfdan was a Viking commander who had etched his name sometime between the 9th and 11th centuries CE when the streets of Constantinople had such a sizable Viking population that they even took over a whole neighborhood, Aya Mamas.

What was interesting about the etched Viking ship is that it had a dragon head, dispelling all other theories about the origin of Halfdan. 

The ship etched isn't dissimilar to the famous Oseberg Viking Ship, uncovered in Norway in the 19th century CE, which has become one of the most recognizable symbols of the Vikings. 

Could it be that Halfdan and his crew made their way to Constantinople on such a magnificent vessel? Erucan seems to think so.

In a mosque that houses elements of paganism, Catholicism, Orthodox Christianity, and Islamic architecture and symbols, the runic inscriptions scrawled by Halfdan over a millennium ago represent just another fascinating cultural chapter to an icon that seems to surpass the bounds of human imagination.

To read more about what the runic alphabet is, read our article here, whilst the National Museum of Denmark has more on "Viking graffiti" here

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