It is the seventh largest body of freshwater in the world, yet it has never been glimpsed by human eyes. Lake Vostok is hidden nearly 4km beneath the wind-blasted surface of Antarctica, a giant sub-glacial pocket which scientists believe could harbour previously undiscovered forms of life, perhaps even bizarre new species of fish.
But the 250km-long lake and its mysterious inhabitants may not remain undisturbed for much longer. A team of Russian scientists is close to penetrating the lake with a bore, dumping 65 tonnes of kerosine lubricant in the process. They have drilled to a depth of 3,600 metres and are about 100 metres away from breaking through the last section of ice to the water beneath.
There are grave concerns among international Antarctic experts that Lake Vostok could be irreparably polluted by the exploration.
The contentious Russian experiment is one of a clutch of activities which are threatening an end to Antarctica's isolation and pristine state.
Once the domain of doughty explorers such as Scott, Shackleton and Amundsen, Antarctica at the beginning of the 21st century is becoming increasingly crowded.
An explosion in tourism, an expansion in the number of scientific bases, a US-built 'ice highway' and plans for air links from Australia and South Africa are all part of a dramatic increase in human activity.
Looming large over the rise in international interest is the prospect of oil, gas and minerals exploration.