Examining a set of bizarre markings that suggest a violent clash between prehistoric beasts; in California, Rob investigates to see if a strange lake is a home to alien life.

Descending into a cave 30 feet beneath Texas in search of evidence of a mass extinction event; heading to Lake Michigan to investigate a Bermuda Triangle-like phenomenon that has caused ships to disappear for centuries.

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

Investigating a cluster of ancient ruins in New England that suggest Europeans arrived in the Americas almost 1,000 years before Columbus; heading to California where a dormant super volcano may be showing new signs of life.

Investigating 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.

A legendary train filled with stolen Nazi gold is said to be hidden in Poland; using cutting-edge technology, Rob Nelson and Stefan Burns explore deep underneath the earth's surface and in abandoned Nazi tunnels in search of the infamous legend.

Priceless gold and silver artifacts are believed to be in fabled lost Temple Treasures of Jerusalem and King Solomon's hidden mines.

Nikola Tesla died before he finished a mysterious invention, but the ground beneath his only remaining lab might hold clues.

A massive supervolcano beneath Naples, Italy, may be on the verge of erupting again, which could have apocalyptic consequences across the planet.

New theories claim that the legendary sunken city of Atlantis actually could have been in the Americas; Rob Nelson and Stefan Burns investigate evidence that might shed more light on one of the world's greatest mysteries.

A strange cave freezes in the summer and melts in the winter; a massive sand dune swallows a small child in an instant.