We visited both of the cities destroyed when Vesuvius erupted in 79 AD: Pompeii and Herculaneum. Pompeii is more well known but Herculaneum is also interesting. While Pompeii was a medium sized trade and industrial center, Herculaneum was more of a resort area. Herculaneum has not been as extensively excavated since there is a modern city on top of the old one, but the part that has been excavated is very interesting.
