Thanks to Tom Williams for tipping me off to this...If you want to go straight underground, click on The Tunnel that Made The Great Escape Possible.
"Electric lighting. A railroad. An air ventilation system. Against incredible odds, the Allied airmen imprisoned at the Nazi POW camp Stalag Luft III secretly engineered these and other technological marvels 30 feet underground in the three escape tunnels they named "Tom," "Dick," and "Harry." They used only tools that they could manufacture themselves out of tin cans, and they scavenged building materials at great risk. When they were done, the airmen carried out one of the greatest mass escapes of all time. Through this interactive map, drawn after the war by one of the POWs, Ley Kenyon, explore the remarkable story of Harry, the 300-foot tunnel that 76 men snuck through during their infamous getaway on the night of March 24-25, 1944."
Stalag Luft III (Stammlager Luft, or Permanent Camp for Airmen #3) was a German Air Force prisoner-of-war camp during World War II that housed captured air force personnel. It was near Sagan, now Żagań in Poland, 100 miles (160 km) southeast of Berlin. The site was selected because it would be difficult to escape by tunnelling, but it is best known for two famous prisoner escapes that took place there by tunnelling, depicted in The Great Escape & The Wooden Horse.
The first prisoners, or kriegies, as they called themselves, to be housed at Stalag Luft III were British RAF and Fleet Air Arm officers, arriving in April 1942. The first compound of the camp was completed and opened in May. USAAF prisoners began arriving in significant numbers in October, 1943, followed by completion of a second and third compound by March 1944, when U.S. officers were separated from their RAF counterparts and housed separately. Eventually the camp grew to approximately 60 acres (240,000 m2) in size and eventually housed about 2500 Royal Air Force officers, about 7500 U. S. Army Air Corps, and about 900 officers from other Allied air forces, for a total of 10,949 inmates, including some support personnel officers...
The "Great Escape"
In January 1943, Roger Bushell led a plot for a major escape from the camp. The plan was to dig three deep tunnels, codenamed "Tom," "Dick," and "Harry." Each of the tunnel entrances was carefully selected to ensure they were undetectable by the camp guards. The tunnel "Tom" began in a darkened corner of a hall in one of the buildings. "Dick's" entrance was carefully hidden in a drain sump in one of the washrooms. The entrance to "Harry" was hidden under a stove.
In order to keep the tunnels from being detected by the perimeter microphones, they were very deep — about 10 metres (30 ft) below the surface. The tunnels were very small, only two feet square (about 0.37 m²), though larger chambers were dug to house the air pump, a workshop, and staging posts along each tunnel. The sandy walls of the tunnels were shored up with pieces of wood scavenged from all over the camp. One main source of wood was the prisoners' beds. At the beginning, each had about twenty boards supporting the mattress. By the time of the escape, only about eight were left on each bed. A number of other pieces of wooden furniture were also scavenged..." More...