Vital for making its waters so 'pure', one theory is that rising underwater methane leaks are killing off the sponge, but is there a silver lining?
International researchers have gleaned these extraordinary hidden scientific secrets by drilling 318 metres into a unique lake in northeastern Siberia.
Locals warned not to use water for baths as authorities urgently check for radioactive or toxic substances.
Norilsk is home to the world biggest mining and metallurgy complex, and is shut off from the world in more ways than one.
Plans for modern Nature Theme Park and Acqua-park on site of old pulp and paper mill that spewed pollution into lake.
Map of shame: Greenpeace highlights junk and debris in dozens of sites across the 'pristine' environment.
Economic crisis to blame for delay in plan to breathe new environmentally-friendly life into former Lake Baikal polluter.
Oil slicks, sewage, industrial waste and rubbish floating sea is harming wildlife and could lead to marine crisis.
Or is it too expensive to put the environment before the need for energy?