The Mauritania Railway is primarily used for transporting iron ore across the Sahara Desert. Construction was completed on this over 430-mile long railway in 1963 and it’s been in use ever since. The actual train is one of the longest and heaviest in the world, stretching 1.8 miles long. This rail line is foundational to the local economies it connects, and is one of the few industrial lifelines across this expansive wasteland. Take a look at its incredible engineering in the beautiful documentary from National Geographic below.