Pompeii
Have you ever been to Pompeii? Wait, do you know about it? It's an ancient Roman city that's been completely covered by ash and pumice after a particularly violent eruption of a nearby volcano, Mount Vesuvius. It's often mentioned together with the city of Herculaneum, which suffered the same fate, but I suppose Pompeii is slightly more famous1.
I was in elementary school when I went there with my family, if I'm not remembering it wrong. I was a kid who loved Greek and Roman mythology, but was very disinterested in history, buying into the notion that it's boring and no one is actually into it. As an adult, I see it's very weird to like mythology and ignore history, but it stems from a lie I believed throughout all my school years: history is not about people. "We study history not to repeat past errors"? Yeah, but we're not like people in history. It feels very stupid to write this. Are we really letting kids believe it?
Let's get back to Pompeii. Nowadays, together with Herculaneum, it's an open-air museum: the cities have been preserved almost perfectly at the time of the eruption, and you can see plenty of people frozen in time (as the volcanic ash has pretty much turned them into stone) at the moment of their death. Morbid, isn't it? You can walk around and witness a woman cradling her child, trying to protect them from the eruption, or a couple holding hands, or a dog trying to free itself from its chain. But the whole city is mostly intact too! It's something else, to visit a ghost town from 79 A.D.

When I was a kid, I was so impressed to see that dog owners of the past also had "Beware of the Dog" signs. This "Cave Canem" mosaic was at the entrance of the house of a poet! That's kind of fancy, isn't it? And there's plenty of writing on walls too! You can check them all out on the Ancient Graffiti Project site.
My personal favourite is "Apollinaris medicus Titi Imperatoris hic cacavit bene". Actually, this one is in Herculaneum, but it stuck with me so much I know it by heart and it's never left my mind. People have pooped since ancient times, and have had the concept of "taking a good shit" since forever...
If this was a movie, I'd say after this my life had changed, I started loving history, and I became a scholar or something. As I previously mentioned, I did not: school has often discouraged me (and many others) in loving a subject to focus more on results and, at worst, rote memorization, and I wasn't as lucky to ever get a good history teacher2. But I often thought back to Pompeii, and I'd like to get back some day to visit again.
How do you feel thinking that everything around you carries the traces of someone else?