Rob Nelson investigates the mysterious pattern of rocks at the bottom of Lake Michigan known as Underwater Stonehenge. At the notorious Alcatraz prison, Rob uses state-of-the-art technology in search of rumored escape tunnels.

Rob investigates ancient ruins in New England that suggest Europeans arrived in the Americas almost 1,000 years before Columbus. Then, he heads to California where a dormant super-volcano may be showing new signs of life.

Rob Nelson heads to California to investigate a network for major fault lines that could set off an unprecedented mega-quake. Then, he explores a mysterious sinkhole that some believe is an endless pit to the center of the Earth.

Rob descends into a cave 30 feet beneath Texas in search of evidence of a mass extinction event. Then, he heads to Lake Michigan to investigate a Bermuda Triangle-like phenomenon that has caused ships to vanish for centuries.

Rob Nelson examines a set of bizarre markings that suggest a violent clash between prehistoric beasts. In California, he investigates if a strange lake is a home to alien life.

Rob Nelson hunts for a legendary mass grave that could expose a dark secret of America's industrial past. High in the mountains, a giant lake is mysteriously disappearing, and Rob uses cutting-edge technology to find out why.

Rob Nelson explores mysterious tunnels beneath Denver's airport and capitol building to investigate rumors of a secret organization operating below. In Ohio, he tries to uncover the ancient secrets of a mound shaped like a serpent.

Rob Nelson investigates rumors of a secret underground escape route used by the infamous gangster Al Capone. In Washington state, Rob tries to uncover who -- or what -- built a vast landscape of earthen mounds in Washington state.