So imagine my complete shock when I stumbled across this passage from an article by Peter Head:
“Gehenna is presented as diametrically opposed to ‘life’: it is better to enter life than to go to Gehenna. . .It is common practice, both in scholarly and less technical works, to associate the description of Gehenna with the supposedly contemporary garbage dump in the valley of Hinnom. This association often leads scholars to emphasize the destructive aspects of the judgment here depicted: fire burns until the object is completely consumed. Two particular problems may be noted in connection with this approach. First, there is no convincing evidence in the primary sources for the existence of a fiery rubbish dump in this location (in any case, a thorough investigation would be appreciated). Secondly, the significant background to this passage more probably lies in Jesus’ allusion to Isaiah 66:24.” (“The Duration of Divine Judgment in the New Testament” in The Reader Must Understand edited by K. Brower and M. W. Ellion, p. 223, emphasis mine)
“Ge-Hinnom (Aramaic Ge-hinnam, hence the Greek Geenna), ‘The Valley of Hinnom,’ lay south of Jerusalem, immediately outside its walls. The notion, still referred to by some commentators, that the city’s rubbish was burned in this valley, has no further basis than a statement by the Jewish scholar Kimchi (sic) made about A.D. 1200; it is not attested in any ancient source.” (p. 376n.92)
“The traditional explanation that a burning rubbish heap in the Valley of Hinnom south of Jerusalem gave rise to the idea of a fiery Gehenna of judgment is attributed to Rabbi David Kimhi’s commentary on Psalm 27:13 (ca. A.D. 1200). He maintained that in this loathsome valley fires were kept burning perpetually to consume the filth and cadavers thrown into it. However, Strack and Billerbeck state that there is neither archeological nor literary evidence in support of this claim, in either the earlier intertestamental or the later rabbinic sources (Hermann L. Strack and Paul Billerbeck, Kommentar zum Neuen Testament aus Talmud and Midrasch, 5 vols. [Munich: Beck, 1922-56], 4:2:1030). Also a more recent author holds a similar view (Lloyd R. Bailey, “Gehenna: The Topography of Hell,” Biblical Archeologist 49 : 189. (p. 328n.17)
Looks convincing to me. I'll place that common belief in the 'not proven' basket.
HT: BiblePlaces blog