A rusty piece of cable that has become embedded in the bark of a yellow poplar tree (upper photo) opposite the entrance to Sand Cave (lower photo) in Cave City, Kentucky, is seen in this Jan. 26, 1965 photo. The photo was taken to commemorate the 40th anniversary of the operation to try to free Floyd Collins, a 35-year-old cave-explorer who was trapped in the cave. Collins was found dead on the 18th day of his entrapment. The cave now is part of Mammoth Cave National Park. (AP Photo/RH)