How often have you visited a historical site and been stunned that someone would be so selfish as to carve their names into it? This type of vandalism might seem to be the product of modern narcissism. But in reality, the human urge to leave their mark goes back millennia.

10. Medieval Church Graffiti

The medieval church was powerful in a way that today's churches can only dream of. We might imagine that this would lead to them being inviolable, but even a cursory glance at medieval churches will show how untrue this is. Any surface in reach is likely to be marked in some way—in either pious devotion or distracted doodling. Some of the graffiti looks as if it was inspired by the sermons the vandals were listening to. Crosses, angels, and the Virgin Mary all appear etched into the walls and pillars of churches. Perhaps this was a form of worship for those unable to speak the Latin of the mass or too illiterate to write out their faith. Other forms of graffiti speak of graffiti as prayer. Medieval ships are a common motif. It has been suggested that these may have been made as a form of prayer of protection for those on the sea. Portraits of individuals also turn up. Kings and queens often feature, as do saints, but images of common men and women can tell us lots about the clothes and appearance of people who would otherwise be forgotten.

9. Pompeian Prostitutes

Many depictions of Ancient Rome show it as a glittering citadel of white marble. In fact, the Romans were as earthy and real as any living people. The proof of this can be seen engraved in the walls of Pompeii. The ancient city was destroyed by a volcanic eruption that ironically preserved it far better than any other Roman site. Pompeii boasted an impressive number of brothels to cater to all tastes. These houses can be recognized from the stone beds packed into tiny rooms and erotic frescos showing guests what was on the menu. When customers staggered out into the street, or even while they were engaged in their cubicles, they liked to leave notes about the joys of their visit. "Hic ego puellas multas futui," one man wrote—"Here I have f—ked many girls." Anothers left a review: "Murtis bene felas"—"'Myrtis, you suck well." "Rufa ita vale quare bene felas."—"Rufa, may life be as good as your sucking." Not all customers were as pleased with their service: "Sabina felas no belle fasces."—"Sabina you are sucking it, but not well." One man seems to have become disillusioned with the whole profession, as this graffito on a brothel shows: "Weep, you girls. My penis has given you up. Now it penetrates men's behinds. Goodbye, wondrous femininity!"

8. Vikings—Hagia Sophia

Sometimes, graffiti can be deeply revealing about the world of those who made it, and sometimes, it is more revealing of human nature itself. The Hagia Sophia in Istanbul is one of the grandest religious structures in the world. It was begun in 532 and has been a church, a mosque, and museum over the course of the centuries. It has also been a writing pad for Vikings. On a marble banister is a string of runes left at some point in the ninth century. While the years have worn it away, the name Halfdan can still be made out. One reading of the rest of the inscription could be that it simply says "Halfdan was here." In a different part of the building, another runic graffito has been found, badly eroded. All that can really be read is the name Arni or Ari—another Viking with a fondness for leaving his own name in stone. It seems likely that these men served in the Varangian Guard, an elite corps of troops used by the Byzantine emperors. This body was made up mostly of Scandinavians, who apparently brought their runic writings with them.

7. Tower Of London

When people are locked up for long periods, graffiti can be a tempting way to pass the time. Just check out the desks in detention room. The Tower of London is a castle that has long been used by English monarchs as both a place of safety for themselves and a place to keep troublemakers out of the way. These noble prisoners often took their chance to leave a reminder of their existence in case they never walked out of the prison. Some of the graffiti is simply a name. A "remember me." Others are whole sentences such as a Latin inscription left by Philip Howard, Earl of Arundel in 1587, which says, "The more affliction we endure for Christ in this world, the more glory we shall get with Christ in the world to come." Noble crests and insignia also abound on the walls. Other prisoners seem to have undermined their defenses with their graffiti. One man who was imprisoned on a charge of sorcery took the time to scratch a detailed horoscope in his cell.

6. Alexamenos Graffito

In 1857, an excavation on the Palatine Hill in Rome turned up a piece of graffito in the plaster of a wall. We've already seen that the Romans were not shy with the things they were willing to write on a wall, but it seems they were not afraid of blasphemy either. The Alexamenos Graffito, dating from around AD 200, may be the earliest depiction of Jesus—and it is not flattering. The Alexamenos Graffito shows a figure hanging from a cross with a man at the base looking up. Text, in Greek, says "Alexamenos worships his god." What stops this being a standard image of the crucifixion is that the person on the cross has the head of a donkey. This shows some of the aggression toward the relatively new Christian religion that must have existed at the time. Tertullian, an early Christian author, refers to the idea that "our god is the head of an ass." The graffito is also an important source on the act of crucifixion as it was made at a time when people would have seen criminals nailed up by the roadside.