The wilderness lines that have pushed the frontiers of human endeavour into previously unknown territories, solving a set of complex problems along the way.

Since their rise in the 19th Century, railways have been at the forefront of modern engineering and transport, conquering dizzying altitudes, wilderness, seas and cities.

Engineering that has overcome some of the greatest mountain ranges to create innovative railways, including a tunnel in the Swiss Alps and a zig-zag railway in Ecuador.

How some of our greatest railways have challenged engineering's finest minds in their efforts to conquer the planet's waterways, including a tunnel beneath the English Channel.

A look at the planet's most incredible metropolitan railways, and how they help people solve distinctly urban problems. Including a project to upgrade New York's transit system.