AVERNUS  , a

lake of Campania, Italy, about 11 m . N. of Baiae . It is an old volcanic crater, nearly 2 M. in circumference, now, as in Roman times, filled with water . Its depth is 213 ft., and its height above sea-level 31 ft.; it has no natural outlet . In ancient times it was surrounded by dense forests, and was the centre of many legends . It was represented as the entrance by which both Odysseus and Aeneas descended to the infernal regions, and as the abode of the Cimmerii . Its Greek name, "Aopvos, was explained to mean that no bird could fly across it . Hannibal made a pilgrimage to it in 214 B.C . Agrippa in 37 B.C. converted it into a naval harbour, the Portus Julius; joining it to the Lacus Lucrinus by a canal, and connecting the latter with the sea, he reduced the distance to Cumae by boring a tunnel over 2 m. in length, now called Grotta della Pace, through the hill on the north-west side of Lake Avernus . After Sextus Pompeius had been subdued, the chief naval harbour was transferred to Misenum . Nero's works for his proposed canal from Baiae to the Tiber (A.D . 64) seem to have begun near,Lake Avernus; indeed, according to one tl}eory, the Grotta della Pace would be a portion of this canal .

On the

east side of the lake are remains of baths, including a great octagonal hall known as the Temple of Apollo, built of brickwork, and belonging to the 1st century . The so-called Grotto of the Cumaean Sibyl, on the south side, is a rock-cut passage, ventilated by vertical apertures, possibly a part of the works connected with the naval harbour . To the south-east of the lake is the Monte Nuovo, a volcanic hill upheaved in 1538, with a deep extinct crater in the centre . To the south is the Lacus Lucrinus . See J . Beloch, Campanien (2nd ed., Breslau, 1890), pp . 168 seq . (T .