Maybe that's because it's also one of the world's steepest roads, chiseled into the mountain by local villagers. The Guoliang Tunnel is located in the Taihang Mountains in China's Henan Province ...

But none were quite as formidable as the snowy granite mountain range rising east ... Drifts clogged the entrance to every tunnel, turning many workers into full-time shovelers.

Below Detroit's streets is a network of tunnel systems almost as elaborate ... From the salt mines used to launch the city into economic prosperity at the start of the 20th century to the remnants ...

If a tunnel must exist, why not make it beautiful? The folks responsible for Norway's Fyllingsdalstunnelen – a tunnel ...