On a balmy Thracian sunday some 1,100 years ago, during a liturgy given in the massive basilica of Hagia Sophia in Constantinople, possibly during the solemn, laborious prayer of the Anaphora, a bored soldier carved his name into the white marble parapet that surrounds the balcony of the church’s upper gallery.

The letters he carved, however, weren’t Greek; this wasn’t a native warrior, but a Viking mercenary from the Scandinavian lands of the north. His runic inscription is still visible today. They read, approximately, “Halfdan carved these runes,” or “Halfdan was here,” a familiar sentiment shared by crude etchings across the millennia. A transparent plastic slab protects the inscription, which can be found in the gallery on the second floor of the basilica.

In the city of Venice lies a famous Greek lion that has borne witness to epic wars between empires, survived a barrage of 17th-century cannon fire, and felt the expert hands of Viking rune carvers. Though the casual or uninformed observer might easily presume the statue to be a fine example of Italian craftsmanship, perhaps of the Renaissance era, the lion was actually carved thousands of years ago in the historic port of Piraeus, near Athens.

Even more unexpectedly, across the shoulders and the flank, you will find the mark of the Vikings. Or, to be more precise, a set of unique runes thought to have been carved by the Varangian Guard, a group of Vikings that served as an elite unit of the Byzantine Army from the tenth to the 14th century.