Dara O Briain continues his journey across Italy, to uncover what happens when volcanoes turn from natural wonders into human disasters.In this episode, he leaves Stromboli and travels to mainland Italy. With volcanologist Dr Dougal Jerram, he learns about a deadly phenomenon known as a pyroclastic flow. This searingly hot cloud of ash and debris can reach speeds of hundreds of miles per hour and will obliterate everything in its path.In Naples, Dara explores the story of Mount Vesuvius and its 79AD eruption. This disaster buried the Roman town of Herculaneum under layers of ash and rock. He meets Professor Luigi Capasso, who studies the skeletal remains of Herculaneum's final residents. Luigi's work reveals how quickly and violently these people died.Scaling Mount Vesuvius, Dara visits its enormous crater. Layers of rock and ash show the volcano's explosive history. He then meets cultural expert Dr Elisabetta Moro. She explains how living near an active volcano has shaped the culture and mindset of Naples.With an active volcano on their doorstep, the people of Naples need protection. At the Vesuvius Observatory, Dara meets Dr Giovanni Macedonio. He explains how technology tracks the volcano 24/7, providing vital warnings to the million people living nearby.Finally, Dara visits Campi Flegrei—a supervolcano hidden beneath the city. Dr Antonio Costa explains how this massive system threatens 500,000 people living above it. It's so big its next eruption could not only devastate Naples but disrupt the global climate.