An ancient network of channels which may have taken up to 2.3 million years to form has been found under the Jakobshavn Glacier in Greenland.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/ancient-river-system-found-under-greenland%E2%80%99s-ice-sheet
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/big-news-network
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-resources
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rivers
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/greenland