This is a view looking down into the hole drilled for the IceCube strings. The sphere you see is a digital optical module about 17 meters down. The entire hole is about 2.5 kilometers (about 1.5 miles) deep. It goes about 50 meters before it is filled with ice-cold water for the remaining 2,400 meters. The water eventually freezes around the string of DOMs, sealing them in forever. Near the Amundsen-Scott South Pole Station, Antarctica.
Credit to read: Photo by Casey O'Hara (PolarTREC 2009/2010), Courtesy of ARCUS