Neapolis, Naples, was situated on the W. slope of Mt. Vesuvius and on the banks of the small stream Sebethus. It was founded by the Greeks of Cumae, and was named Neapolis, "New City," in contradistinction to Palaepolis, "Old City," which had been previously established, probably on the hill of Pausilypus. The name of Parthenope appears to have originally belonged to Palaepolis, but was subsequently transferred to Neapolis.
Source: wiktionary