It has been about 200,000 years since the last massive eruption of Campi Flegrie near Naples, Italy (one of the most densely populated areas of the world). Campi Flegrie in Italian means "burning fields".

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Scientist report that Campi Flegrie, which lies under the feet of 500,000 people in Italy, may be waking up and approaching a "critical state".

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Scientist at the Italian National Institute of Geophysics in Rome think the magma inside Campi Flegrie is approaching the critical degassing pressure. Scientists are observing accelerating ground deformation and heating.

Threat Level Elevated

The Italian government has raised the threat level for this super-volcano from green to yellow as scientists are continuing to monitor the area.

Full Article

One of Earth's Most Dangerous Super-volcanoes Is Rumbling, National Geographic, 22 December 2016, by Brian Clark Howard

Campi Flegrei Super-volcano "The Risk Of Eruption Is High"

The super-volcano has been monitored for many years. Here is a video from 14 October 2015:

Additional Sources

Campi Flegrei, secondo i geologi ci sono “segnali preoccupanti”