The Campi Flegrei ("burning fields") or Phlegrean Fields is a large, 13-km-wide nested caldera located under the western outskirts of the citiy of Naples and under the Gulf of Pozzuoli. It contains many volcanic centers (cinder cones, tuff rings, calderas) that have been active during the past 30-40,000 years. The volcanic field has been the site of some extremely violent eruptions in the past, although the few ones that occurred during historic times were small events. Today, there is no sign of imminent reawakening of activity, although there are abundant signs of the presence of a still active magma chamber in the forms of solfataras, warm springs, gas emissions etc. In particular, the Campi Flegrei is infamous for its frequent episodes of major ground deformation in the form of large-scale up- and downlift of the ground (bradisism, see below).