The Über Pit of Voles, also sometimes called the Pit of Rabid Horny Weasels, is more commonly known as Adult-FanFiction.org (AFF). While generally the fics there are written by and for an older audience, this does not mean that the quality of the writing increases. It simply means that urple prose is more frequent and geographical inaccuracies are replaced with anatomical inaccuracies. In short, it is a more explicit version of the Pit of Voles (although AFF and FanFiction.net are not affiliated). Many fics from GAFF are culled from its pages, though only a few PPC'd fics originated there.
The Über Pit was originally AdultFanFiction.net, but it moved for unknown reasons.