An underground tunnel network long rumored thanks to drawings by Leonardo da Vinci under Milan’s Sforza Castle are proven to ...

After centuries of speculation, archaeologists in Peru have confirmed the existence of an underground tunnel network ... (AFP via Getty Images) Under Inca rule, Cusco was developed into a complex ...

Built on a limestone foundation, Valletta housed defense systems in deep tunnels during WWII that saved Malta and Allied ...

clodio/iStock Editorial / Getty Images Plus ... buried a foot or more under the ground. Some of these, the researchers say, can be linked to secret military tunnels that can also be seen ...