The Wooden Horse

As described in his novelization of the true events The Wooden Horse, Stalag Luft III was designed to be a highly escape-resistant camp. Tunnelling in particular was made harder by the use of numerous environmental and technological solutions: the perimeter fence was placed some distance from the huts, necessitating longer tunnels; the soil in the chosen location changed colour markedly when dry, making disposal of freshly dug tunnel soil difficult; and the Germans employed seismographs to measure vibration caused by digging.