Lake Vostok

In the 1970s, a huge lake (about the size of Lake Ontario) was discovered in Antarctica, under miles of glacier ice. It has been separate from the rest of the world for a very very long time. The discovery in recent years of life under more extreme conditions than had been thought possible has led to speculation that life may well indeed exist down there, and give some idea of whether and how life might exist in the underground oceans of Jupiter's moon Europa (inconclusive evidence suggests such oceans).

BBC article: http://news.bbc.co.uk/hi/english/sci/tech/newsid_458000/458586.stm

The National Science Foundation report on exploring it (from a large 1998 workshop): http://www.ldeo.columbia.edu/vostok/

The question about whether to go ahead with exploration now: http://www.asoc.org/currentpress/lakev.htm

Google search: http://www.google.com/search?q=%22Lake+Vostok%22

Also see SpaceScience?