One of the things Kagoshima is best known for is its proximity to Sakurajima, an active volcano on a nearby island (or what used to be an island — the lava from a 1914 eruption actually connected it to the mainland).
Obviously if you’re in Naples, you’ve gotta go to Pompeii — it’s a quick, cheap train ride away from the city, and it’s an interesting enough piece of history to be common knowledge around the world. You’d be crazy to miss it.