By Sille Veilmark
The rocky chamber in the world’s biggest cave system, Mammoth Cave, is dimly lit. The echoing chatter from 107 mouths dies out as the flock approaches a slim man with red beard. He is wearing a stiff park ranger hat, and the glue in his hiking shoes are not holding the sole together completely anymore. The air is cold, dry, and tastes slightly of stone. Visitors over the years have burned their names in the flat cave ceiling with torches, in a font that looks like a typewriter.