Campi Flegrei is much bigger than the nearby Vesuvius. It last erupted in 1538.
Italy is planning for possible evacuations from a super volcano near Naples.
After months of repeated earthquakes, the government is putting measures in place to ensure the area is ready to face stronger tremors or eruptions.
Detailed plans are being drawn up to evacuate tens of thousands of people living near Campi Flegrei.
Where is Campi Flegrei volcano?
Campi Flegrei, or Phlegraean Fields from the Greek word for 'burning', lies some 20 kilometres from Naples - the gateway to the picturesque Amalfi Coast.
The caldera is dotted with 24 craters and is much bigger than the nearby Vesuvius, which destroyed the ancient Roman city of Pompeii in 79 AD.
Why is Italy planning for possible evacuations near Naples?
The Italian government is planning for a possible mass evacuation of tens of thousands of people who live around the Campi Flegrei super volcano, officials said in early October.
The new measures, which include a scheme to check on the strength of buildings in the area after months of repeated earthquakes, were to be discussed at a cabinet meeting later in the day, a government statement said.
Campi Flegrei is dotted with towns and villages, including Pozzuoli, Agnano and Bacoli, which have a combined population of more than 500,000.
It has been jolted by more than 1,100 earthquakes in the last month alone, including a 4.0 trembler on Monday and a 4.2 magnitude quake last week - the strongest in the area for four decades.
Is Campi Flegrei likely to erupt?
Experts say the increased seismic activity is probably linked to a phenomenon known as bradyseism, when the earth rises, or falls, depending on the cycle, caused by the filling or emptying of underground magma chambers.
There is not an imminent threat of an eruption, most volcanologists say, but with the ground currently rising by 1.5 cm a month, there is concern over the impact on local buildings.
Italy's Civil Protection Minister Nello Musumeci said this week evacuations would only be triggered in case of "extreme necessity".
The cabinet is also expected to direct more resources to local civil protection agencies to ensure they can swiftly intervene in case of emergency and to fund a communication campaign to raise public awareness, Musumeci said.
Local media reported that a group of hospitals in the area would start evacuation tests to make sure they are ready to face stronger quakes or eruptions.
When did Campi Flegrei last erupt?
The last time Campi Flegrei suffered a comparable burst of earthquakes was in the 1980s. On that occasion, some 40,000 people were temporarily evacuated from nearby Pozzuoli.
The last significant eruption was in 1538. One of its biggest eruptions took place 39,000 years ago and might have led to the extinction of Neanderthal man, researchers say. Magma from that blast has been found in Greenland, some 4,500 km away.
What happens if the Campi Flegrei volcano erupts?
Should an eruption occur, an evacuation plan will be triggered. This stipulates that residents will be moved out of the area using private or public transport within three days.
The risk levels of green, yellow, orange and red are reviewed monthly. The alert level in Pozzuoli is currently yellow.
Local residents also receive text alerts when there is a tremor measuring a magnitude of 1.5 or greater on the Richter scale.