Humans have always wanted to go through obstacles instead of around them. The first tunnels were simple affairs, dug with basic tools and bare hands. Ancient civilizations somehow managed to create underground passages without modern equipment - just imagine the labor involved in chiseling through solid rock with primitive tools!
Today's tunnels look nothing like those early attempts. Engineers now command massive tunnel-boring machines that chew through mountains as if they were made of butter. These mechanical beasts can create perfectly round passages in a fraction of the time it once took hundreds of workers.
These 15 photos reveal just how far we've come in our quest to reshape the earth below our feet.
Related: Astounding! These Enormous Tunnels Weren't Dug by Humans!
