Mount Etna. Mount Etna, or Etna, is an active stratovolcano on the east coast of Sicily, Italy, in the Metropolitan City of Catania, between the cities of Messina and Catania. It lies above the convergent plate margin between the African Plate and the Eurasian Plate. It is the highest active volcano in Europe outside the Caucasus and the highest peak in Italy south of the Alps with a current height of 3,326 m, though this varies with summit eruptions. Etna covers an area of 1,190 km 2 with a basal circumference of 140 km. This makes it by far the largest of the three active volcanoes in Italy, being about two and a half times the height of the next largest, Mount Vesuvius. Only Mount Teide on Tenerife in the Canary Islands surpasses it in the whole of the European-North-African region west of the Black Sea. In Greek Mythology, the deadly monster Typhon was trapped under this mountain by Zeus, the god of the sky and thunder and king of gods, and the forges of Hephaestus were said also to be underneath it. Mount Etna is one of the world's most active volcanoes and is in an almost constant state of activity. The fertile volcanic soils support extensive agriculture, with vineyards and orchards spread across the lower slopes of the mountain and the broad Plain of Catania to the south. Due to its history of recent activity and nearby population, Mount Etna has been designated a Decade Volcano by the United Nations. In June 2013, it was added to the list of UNESCO World Heritage Sites. In Classical Greek, it is called, a name given also to Catania and the city originally known as Inessa. In Latin it is called Aetna. It is also known as Mungibeddu in Sicilian and Mongibello or Montebello in Italian. According to another hypothesis, the term Mongibello comes from the Latin Mulciber, one of the Latin names of the Roman god Vulcan. Another theory is that Mongibello came from the Italian word monte plus the Arabic word jabal, both meaning mountain. Today, the name Mongibello is used for the area of Mount Etna containing the two central craters, and the craters located southeast and northeast of the volcanic cone. The name Mongibel is found in Arthurian Romance, as the name of the otherworld castle of Morgan le Fay and her half-brother, King Arthur, localised at Etna, according to traditions concerning them derived from the stories told by the Breton conteurs who accompanied the Norman occupiers of Sicily.What were originally Welsh conceptions concerning a dwarf king of a paradisal, Celtic underworld became attached to the quasi-historic figure of Arthur as Ruler of the Antipodes and were then transplanted into a Sicilian milieu, by Bretons impressed by the already otherworldly associations of the great, volcanic mountain of their new home. Mediaevalist Roger Sherman Loomis quotes passages from the works of Gervase of Tilbury and Caesarius of Heisterbach featuring accounts of Arthur's returning of a lost horse which had strayed into his subterranean kingdom beneath Etna. Caesarius quotes as his authority for the story a certain canon Godescalcus of Bonn, who considered it a matter of historical fact of the time of Emperor Henry's conquest of Sicily circa 1194. Caesarius employs in his account the Latin phrase in monte Gyber to describe the location of Arthur's kingdom. The Fada de Gibel of the Castle of Gibaldar appears in Jaufre, the only surviving Arthurian romance in the Occitan language, the composition of which is dated to between 1180 and 1230. However, in Jaufre, while it is clear from her name that the fairy queen in question is Morgan le Fay, the rich underworld queendom of which she is the mistress is accessed, not through a fiery grotto on the slopes of Etna, but through a 'fountain'-a circumstance more in keeping with Morgan's original watery, rather than fiery, associations, before her incorporation into the folklore of Sicily. For another Sicilian conception of the fairy realm or castle of Morgan le Fay-see Fata Morgana re. an optical phenomenon common in the Strait of Messina. Volcanic activity first took place at Etna about 500,000 years ago, with eruptions occurring beneath the sea off the ancient coastline of Sicily. About 300,000 years ago, volcanism began occurring to the southwest of the summit, then activity moved towards the present centre 170,000 years ago.