My first experience with the underground tunnel system in Denton County was in the mid-seventies. I was on my way to an afternoon keg party out of town and “across the tracks”. I drove past a large 12’x20’ piece of concrete lying in the pasture. This huge slab did not drop from the sky or fall from a truck. I was told it was poured in place to seal an abandoned air shaft that was a part of a huge underground tunnel system throughout Denton County. This unforgettable slab burned into my memory and piqued my curiosity. This slab lying just across the tracks is what ultimately lead me to pursue extensive research of the underground tunnel system lying beneath the Denton County.