Mt. Vesuvius isn’t the only area of volcanic interest near Naples, Italy.

The "Vulcano Solfatara" is just some 6 miles or so to the west of Naples. It is considered to be an inactive volcano and is part of the volcanic region known as the Phlegrean Fields. Even though this area is considered to be dormant, the European Union has a sophisticated satellite monitoring system in place for this area and Mt. Vesuvius to detect any unusual earth movement. Prior to the eruption of Vesuvius in 79 A.D. this area was already known to the Romans and is famous for its steaming jets of sulphurous vapour at temperatures well above the boiling point. Those areas are roped off so tourists can’t get too close, but you can feel the heat and certainly smell the sulphur content in the air.

On one side of the Solfatara you find the entrance to hell and purgatory, which were used as "natural" saunas at one time that provided chambers for the inhalation of sulphurous air. Breathing sulphurous air was considered to be helpful for respiratory illnesses. I guess you were happy to be still breathing after having that smell in your nostrils for who knows how many minutes. The area is also known for small "volcanoes" of boiling mud. The ground level rises and falls in a slow cyclical pattern that scientists call bradisism, in contrast to the rapid movement caused by a volcanic eruption or an earthquake.