Underground giants: our six most impressive tunnel systems

When Did Humans Become a Burrowing Species? - Atlas Obscura

New quantum scanners detect underground tunnels with uncanny accuracy – Matthew Griffin

Six Incredible Man-Made Underground Structures in the World

Prehistoric Giant Ground Sloths Dug Enormous Underground Tunnels

Inside the biggest Hamas tunnel ever found: Israel releases video from giant underground labyrinth that was built by terror chief's brother and spans 2.5 miles beneath war-torn Gaza

Extending Munich's Underground Rail System

TIL there are hundreds of 1000-year-old underground tunnel systems in Bavaria, and nobody really knows who built them or what they're for. : r/todayilearned

The Israel-Hamas Tunnel War Will Be Like No Other

Massive Tunnels Dug by Ancient Sloths Big as Elephants.

Inside the huge London super sewer designed to fight river pollution

The world's most beautiful tunnels