From the World Heritage inscription:
When Vesuvius erupted on 24 August AD 79, it engulfed the two flourishing Roman towns of Pompei and Herculaneum, as well as the many wealthy villas in the area. These have been progressively excavated and made accessible to the public since the mid-18th century. The vast expanse of the commercial town of Pompei contrasts with the smaller but better-preserved remains of the holiday resort of Herculaneum, while the superb wall paintings of the Villa Oplontis at Torre Annunziata give a vivid impression of the opulent lifestyle enjoyed by the wealthier citizens of the Early Roman Empire.
I had always wanted to visite Pompeii and I had my chance this year when the Carnival Magic stopped in Naples. Unfortunately, I was on a tour bus along with several thousand other people who all hit the site at the same time and Pompeii was packed. It really took away from the experience. If you want to see a Roman city which is almost as intact as Pompeii I’d suggest visiting Ostia Antica just outside of Rome. Very few people go there and you can see much of what you can in Pompeii. Likewise, visiting the nearby city of Herculaneum might be a much less busy choice.
View my complete list of UNESCO World Heritage Sites