Impossible Railways

Every day cities around the world rely on the railway to keep them moving. Whether it's commuters travelling to work, tourists seeing the sights or goods going to market, trains take care of them all. This episode takes a closer look at the planet's most incredible metropolitan railways and explores how they help us solve our distinctly urban problems.

From the planet's deepest jungles to its sprawling deserts and mightiest mountains, railways have been instrumental in helping us conquer them all. This episode explores the wilderness lines that have pushed the frontiers of human endeavour into previously unknown territories, solving a set of complex problems along the way. Whether it's a vast canyon spanning trestle bridge in the depths of the San Diego desert, a train that travels through a mountain to reach one of Switzerland's most imposing peaks or the incredible story of prisoners of war battling to build a now infamous jungle railway, they all exist as proof that engineers can overcome the very wildest challenges on Earth.

Railways encounter a multitude of challenges, but among the most demanding of them all comes when faced with crossing the valleys, waterways and canyons that often stand in the way of their progress. This episode of the brilliant documentary series investigates how the most incredible bridges from around the world help to solve a series of spanning problems. From Scotland's iconic Forth Bridge to a vertigo-inducing viaduct in rural New Zealand and an innovative mechanical lift span in Staten Island New York, they each demonstrate an inspired engineering solution that allow trains to overcome any obstacles that might stand in their way.