Byzovaya, a Russian site in the western foothills of the Polar Urals, may have been one the last refuges of Neanderthals according to research by Ludovic Slimak at France's Université de Toulouse le Mirail. Palaeolithic sites in the Russian far north have been long considered an Arctic expansion of modern humans. However at Byzovaya, the stone tools are directly comparable with Mousterian 'toolkits' that so far have been exclusively linked with Neanderthal populations in Europe.
These findings are significant first because they may represent the latest surviving Neanderthals anywhere in the world at 33,000 years ago. Secondly, because at such an extreme northern latitude they contradict the hypothesis that neanderthals died out because they couldn't adapt to the harsh cold and environmental changes of periglacial Europe. The site has yet to yield any human or Neanderthal remains, so it cannot be assigned with certainty to either modern humans or Neanderthals until such bones or DNA are found, but the technological evidence is compelling.
Further reading here and here, and the original research article.