Luft III was a World War II prison set up by Germans at Sagan, 100 miles south-east of Berlin, to hold 10,000 PoWs, It had a size of 59 acres, with 5 miles of perimeter fencing.  The Germans had planted seismographs in the ground every 33 feet so that they could detect the sounds of tunneling. They also had raised the prison huts off the ground on stilts so that they could observe suspicious digging activity. There was a huge trench around the entire prison to form yet another barrier between the prisoners and freedom. Despite all these measures, Stalag Luft III saw one of the biggest mass escapes of all time.

Among the inmates in 1944 were scores of talented miners, carpenters, engineers, even physicists and geologists, all of whom were willing to help execute an escape. The Escape Committee was run by a South African airman named Roger Bushell, who devised a plan in 1943 to dig three tunnels, “Tom,” “Dick,” and “Harry.” Fully 30 feet deep, each tunnel would lie beyond the reach of the listening devices. As they dug, the prisoners removed tunnel dirt by trolley, concealed it in the legs of their pants, and later dumped it inconspicuously around the prison grounds. Groups of prisoners took turns guarding the tunnels from the watchful eyes of the Germans and covering for “missing” prisoners when they were underground. Prisoners made escape kit such as compasses from fragments of broken Bakelite gramophone records, melted and shaped and incorporating a tiny needle made from slivers of magnetised razor blades. Real ID papers and passes were obtained by bribery or theft from the guards and copied by forgers. Service uniforms were carefully recut by prisoners. A surprising number of guards proved co-operative in supplying railway timetables, maps, and the bewildering number of official papers required for escapers.

On the 24th of March, 1944, 76 men were able to escape through Harry. Unfortunately, only three of them reached safety. Fifteen were captured and returned to the prison. Eight were sent to a concentration camp (though they ultimately survived the war). The remaining 50, Bushell among them, were rounded up and shot on orders from Hitler himself, who was embarrassed and infuriated by the mass escape.

Reference:

http://www.mapsofworld.com/on-this-day/march-24-1874-illusionist-harry-houdini-is-born-in-budapest

http://www.pbs.org/wgbh/nova/military/history-great-escapes.html

http://www.elsham.pwp.blueyonder.co.uk/gt_esc/