Two miles inside a mountain in Croatia lies the remains of a massive, secret Cold War airbase built to withstand a nuclear war.

Explore the mystery behind why a huge gun was built and abandoned.

Hidden in woods outside Moscow is a Cold War weapon that harnessed electricity into a thunderbolt, designed to protect the city.

In the east China sea, there is an abandoned piece of land. Check out why this island represents one of the greatest engineering achievements of the 20th century.

Located in California, Plank Road is one of the most extraordinary engineering achievements of the early 20th century.

Philip Grossman finds firefighting gear under a hospital in Chernobyl, sending his Geiger counter climbing. He believes burying the gear was the Soviet’s attempt to hide the scope of the disaster.

Philip Grossman goes inside the plant near the massive radio tower he finds maps of the U.S and pictures of mushroom clouds. Was the Duga for protecting Chernobyl from incoming missiles or part of a nuclear offensive?

Survivors who worked at nearby factory report production areas they weren’t allowed to visit. Philip visits and finds the basement full of lab after lab of gas masks, radioactive testing materials and sand.

This sneak peek of Science Channel's new series, starts with Malaysian Airlines Flight 370 which disappeared without a trace in March, 2014.

Modern aircraft are tracked by multiple systems in flight. Transponders connect with radar, and ACARS transmits signals between ground stations and satellites. In MH370, both were turned off; experts believe a person had to do it.

A hacker who worked his way into critical routing, fuel and other avionics over 20 times via in-flight entertainment, believes a smart hijacker could have used the same tactic to re-route Flight MH370 to a top secret location.

Flight MH370 vanished without a trace but with plenty of theories. One is the strong possibility a cargo of lithium-ion batteries, known to spontaneously combust and burn at high temperatures, could have brought the plane down.

60 years ago, scientists discovered evidence of an eruption 3,000 years ago that wiped out an entire city? Could this be evidence of Atlantis?

Two Atlantis hunters use a computer program that analyzes the 51 clues provided by Plato's writing to objectively target a location for the that vanished in a day.

Something spooked nine experienced hikers out of their tent on snowy night to their deaths. Missing clothes, shoes and some bodies horribly disfigured, an expert with their last writings finds nothing pointing to trouble.

Scientists struggle to find a cause for terrifying rogue waves that can happen even on a clear day.