Pompeii is the most famous ruin in the world, and it deserves its fame in a way that is hard to explain until you have walked its streets. In AD 79 Vesuvius erupted for two days, burying the town under about four metres of pumice and ash, and what was left was a Roman provincial city caught mid-sentence, with graffiti on the walls, loaves in an oven and a dog chained in a doorway. The letters of Pliny the Younger describe the eruption from across the bay, and they are the first account of a volcanic event by an eyewitness. Excavations began in 1748, and about two-thirds of the town is now uncovered.
Look for the details: the stepping stones across the streets, worn by cart wheels, the thermopolia, or snack counters, set into the pavement, the painted walls of the Villa of the Mysteries just outside the gate, in a deep red that is still bright, and the plaster casts of people and animals made by pouring plaster into the hollows left in the ash. The amphitheatre, among the oldest in existence, seated about twenty thousand. The UNESCO listing covers also Oplontis and Boscoreale, the villas around the volcano.
The ride into the area is part of the story. From the autostrada the road comes in through the plain of Campania, a flat, fertile land under the cone of Vesuvius, with orchards, greenhouses and the endless urban sprawl of the Naples suburbs. The streets around the ruins are busy and in places rough, and you should take care with parking, since petty theft is a risk. Use a guarded car park near the Porta Marina entrance and take your valuables with you. The summer heat inside the site is intense, and there is almost no shade, so bring a hat and water.
The modern town of Pompei, with about twenty-four thousand people, has fuel, shops and restaurants, and the Sanctuary of the Madonna of the Rosary draws pilgrims. Wine from the slopes of Vesuvius, called Lacryma Christi, is worth tasting. Visit in April, May, October or November, and consider entering as soon as the gates open, when the light is low and the tour groups have yet to arrive. If you have time, ride up the volcano road to see the crater and the view over the bay.