CAMPI PHLEGRAEI(τὰ φλεγραῖα πεδία) was the name given by the Greeks to the fertile plains of Campania, especially those in the neighbourhood of Cumae. The origin of the name was probably connected with the volcanic phenomena of the neighbouring country, which gave rise to the fable of the giants being buried beneath it (Strab. 5. p. 245; Diod. 5.71), though others derived it from the frequent wars of which this part of Italy was in early times the scene, on account of its great fertility. (Plb. 3.91; Strab. l. c.) Pliny considers the Phlegraean plains of the Greeks to be synonymous with what were called in his time the CAMPI LABORINI, or LABORIAE;but the latter term appears to have had a more limited and local signification, being confined, according to Pliny, to the part of the plain bounded by the two high roads leading respectively from Cumae and from Puteoli to Capua. (Plin. Nat. 3.5. s. 9, 18.11. s. 29.) The Greek name, on the other hand, was probably never a local term, but was applied without discrimination to the whole neighbourhood of Cumae. Hence Silius Italicus calls the Bay of Baiae and Puteoli Phlegraei sinus(8.540), and in another passage (12.143), he distinctly connects the legend of the Phlegraean giants with the volcanic phenomena of the Forum Vulcani or Solfatara.
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