Rob Nelson examines a set of bizarre markings on a Colorado ridge.
A secret, underground escape tunnel used by Al Capone is investigated.
Rumors of a secret organization operating beneath Denver are investigated.
Rob Nelson hunts for a legendary mass grave in Pennsylvania.
A phenomenon causing ships to disappear in Lake Michigan is explored.
Fault lines that could trigger a massive earthquake are investigated.
Strange ruins are examined that may have been built by ancient Europeans.
Rob Nelson searches for rumored escape tunnels deep beneath Alcatraz.