Vulsini

Vulsini, also known as Volsini volcano, Vulsini Volcanic District, Vulsini Volcanic Complex and the Vulsinian District, is a circular region of intrusive igneous rock in Lazio, Italy, about 87 km (54 mi) to the north northwest of Rome, containing a cluster of calderas known to have been active in recent geologic and historical times. Potentially they still are active. The Vulsinian region is one of dozens of intrusive circular regions, most smaller than the Vulsinian, arranged in a band from Campania through Lazio, called the Roman Comagmatic Province. A comagmatic province is a geologic area of the same type and age igneous rock deriving from the same crustal magma. The Roman region is post-collisional; that is, the intrusions were not a result of the lateral stresses that created Italy and raised the Apennines, but were subsequent to Italy's creation. The Volsinian is the northernmost region.

• http://en.wikipedia.org/wiki/Vulsini