Avernus was an ancient name for a crater near Cumae(Cuma), Italy in the Region of Campania north of Naples. Within the crater is Lake Avernus (Lago d'Averno). It was believed to be the entrance to the underworld, and is portrayed as such in the Aeneid of Virgil. In later times, the word was simply an alternate name for the underworld. On the shores of the Lake is the grotto of the Cumaean Sybil and the entrance to a long tunnel (Grotta di Cocceio, ca. 800 meters) leading toward Cumae, where her sanctuary was located. There are also the remains of temples to Apollo and Jupiter During the Civil War between Octavian and Pompey, Agrippa tried to turn the lake into a military port, the Portus Julius . A waterway was dug from Lake Lucrino to Avernus to this end. The Port's remains may still be seen under the Lake's surface.