New technology is allowing us to build underground structures that far surpass any building on earth. South Dakota is building a mile deep structure, inside an abandoned gold mine, to study the universe. London is building a "silent" rail network to prevent gridlock. Mexico City is burrowing 39 miles underneath the city to save it from drowning. On this episode: Sanford Underground Research Lab; London Cross Rail and Mail Rail; Mexico City Emisor Oriente.

The past does not give up its secrets easily. Brand-new machines are helping explorers reveal mysteries once thought lost forever. Underwater archaeologists are searching for a World War II Nazi sub that disappeared in U.S waters. In Scotland, researchers are digging up an ancient rock, covered with cryptic markings, that could reveal more about who built Stonehenge. On this episode: German Submarine U-576; Cochno Stone; LIDAR.

A revolution in engineering is making today's technology as outdated as the horse and buggy. On this episode: world's fastest production motorcycle - Lightning LS-218; a "train" faster than the speed of sound - Hyperloop; the world's first nuclear fusion power plant - ITER.

America has a history of building the impossible. Across the nation, a new generation of impressive projects is underway. On this episode: New Tappan Zee Bridge; Los Angeles Subway; New Orleans pump station; Mount Rushmore preservation.

As humans push even further into the world's most extreme environments, the question is: how far can we go? A new breed of tools allows man to face deadly forces once thought impossible. On this episode: polar survival suit; thermal imaging fire fighter mask; big wave surfing emergency vest.

Above the arctic circle, projects are underway that are opening up the arctic to the rest of the world. What does it takes to build in the world's coldest conditions? On this episode: building a nuclear-powered icebreaker in Russia; laying the world's first trans-arctic cable in Alaska; constructing a modern airport on Baffin Island; building a permanent highway in middle of arctic winter.

Throughout history, mankind has built amazing structures, engineered to overcome unique challenges. Now, a new class of super structures are taking on the impossible: the largest moveable building in history, a super-tall skyscraper built to withstand killer earthquakes, a next-generation sports stadium inspired by an ancient Roman temple, and a bridge being raised while it stays open to traffic.

Toppling giants of concrete and steel is dangerous and deadly. In demolition, one mistake can cost you your life. On this episode: imploding a casino; dismantling chemical weapons; tripping a silo.

In the past 50 years, the world's energy use has doubled. In the next 50 years, it will double again. Can we keep up with demand - or will we plunge into darkness? Across the world, engineers are going to extreme lengths to keep the lights on: harnessing the power of the longest river on Earth, tapping into the raging heat of a live volcano, and building one of the largest offshore wind facilities in the world. This is Project Impossible: Battling the Blackout.

Around the world, a new class of superstorms is overwhelming our coasts. If nothing is done, great cities like New York, Venice, and Tokyo will simply disappear. Engineers are fighting back, raising some of the biggest sea defenses in the world. On this episode: Venice flood barrier; Tsunami Machine; Tokyo underground water diversion tunnels; New Jersey storm defense.