A good example is how 1,800 years ago a school bully scratched some graffiti into the wall of his school, & accidentally gave us the first visual depiction of Christ.
The school had been walled up sometime in the 3rd century to support constructions above it.
Among them, they found a graffito apparently mocking one of the students for being part of a strange new religion sweeping the Empire. He was a Christian.
The crudely-scrawled Greek inscription reads "Alexamenos worships his god".
Since the destruction of Jerusalem in 70 CE, Christianity had found its centre in Rome, & spread gradually.
Laws were passed at various times requiring Christians to sacrifice to Roman gods, & they were targeted by at times brutal repressions.
Jesus' donkey head may also refer to a common belief among Romans that Jews & Christians worshipped donkeys, a myth propagated by the writer Apion in the 1st century.
Other candidates for the first visual depiction of Jesus include this 4th-century painting form the Roman catacombs, & this engraved gem amulet.
In another room nearby, someone has scratched another message, in different handwriting: "Alexamenos fidelis", or "Alexamenos the faithful".
But this is one of my favourite stories of people reaching out to us from history & giving us a glimpse of their lives, without even knowing it.