While Pompeii & Herculaneum are pretty incredible to explore in person, visiting the museum in Naples provides a fuller experience because that's where a majority of art and artifacts wound up after excavation. Thus you can get a better sense of who those people were.
In the museum you have your standard paintings, frescoes, statues, relics and, my favorite, the mosaics. But the most memorable gallery by far is what is officially known as the secret room, or perhaps more appropriately the sex chamber.
Upon entering the secret room, the first thing you see are giant stone phalluses. And from there it only gets weirder. There are frescoes depicting couples having sex in various positions, sculptures capturing acts of bestiality, and mysterious humanoid figurines. Don't believe me? Take a look.
Who knew Romans were so kinky?
*SNSFW = sort of not safe for work