Hidden on the back of the National World War II Memorial in Washington, D.C., is an engraving of Kilroy, the ubiquitous graffito that accompanied American GIs through Europe and, later, around the world. Some earlier inscriptions:

Istanbul’s Hagia Sophia has stood since 537, built by Justinian I as the patriarchal cathedral of Constantinople. It wasn’t until 1964 that runic inscriptions were discovered in the southern gallery, apparently engraved by members of the Varangian Guard during the Viking Age. Their meaning isn’t certain, but one may have read “Halfdan carved these runes” and the other “Ári made the runes.” More may yet be found.

The Piraeus Lion, one of four marble lion statues now at the Venetian Arsenal, bears runic inscriptions apparently made by Scandinavians in the 11th century, when it had stood in Athens. One reads, “Asmund cut these runes with Asgeir and Thorleif, Thord and Ivar, at the request of Harold the Tall, though the Greeks considered about and forbade it.” The other reads, “Hakon with Ulf and Asmund and Örn conquered this port. These men and Harold Hafi imposed a heavy fine on account of the revolt of the Greek people. Dalk is detained captive in far lands. Egil is gone on an expedition with Ragnar into Romania and Armenia.”