The Solfatara crater still smolders endlessly today. Located a few meters from the sea, an entrance leads down a tree lined path to a mars-like terrain. The rotten egg smell is inescapable and, depending on the direction of the wind, wafts all the way to the city of Naples. Maybe the seedy reputation of the city didn’t begin in the twentieth century, but already with the ancients when the sulfur stench was believed to be poisonous.

The slopes surrounding the crater puff with sulfur steam. Along one slope, two fumaroles shum their steam at somewhere around 160 degrees Celsius and turn the rocks around it into a copper-gold color. The Italians call these two vents “La Bocca Grande” or “The Big Mouth.” Behind their plume and hiss, a green algae grows that’s considered a biological rarity seen only when high temperatures and high acidity combine together.

In the middle of the crater, the Fangaia or boiling mud lakes sizzle at temperatures between 170-250 degrees Celcius. The mud contains a bevy of gases and minerals that the Romans once harnessed for their hydrothermal spas.

The Romans said that Vulcan, the god of fire, worked here. The crater is also believed to have been the inspiration for Virgil’s description of Hades. Ruins of a Roman bath still exist at the western side of the crater with sulfur wisping out from the bricks.

If visitors stomp on the ground, they’ll hear a hollow sound – evidence that porous caverns exist underneath. Take a stick, dig a small hole into the sand, and put a finger inside to see how hot the earth feels just beneath the surface.

For those who like science, four reflectors dot the sandy terrain. They work with two satellites of the European Space Agency (ESA) to reflect their signals and map the volcano’s ground deformations.