Famed around the world, Campania's Monte Vesuvio is one of the world's most famous volcanoes—and one that, volcanologists warn, may soon erupt. That fact hasn't kept nearly a million people from settling in the mountain's shadow, where the proud cities of Herculaneum and Pompeii once stood. In 1995, the Italian government set aside the entire mountain as a national park, protecting it from encroaching development and building a well-engineered system of footpaths; the walk from the base to the otherworldly crater, with its cliffs of lichen-covered pumice, takes about three hours each way. The park itself has no services, but campsites are available just outside the park at Torre del Greco and Boscotrecase, and there are plenty of hotels nearby.

Famed around the world, Campania's Monte Vesuvio is one of the world's most famous volcanoes—and one that, volcanologists warn, may soon erupt. That fact hasn't kept nearly a million people from settling in the mountain's shadow, where the proud cities of Herculaneum and Pompeii once stood.