Underground warfare may seem like an ancient tactic, but it's still very much in use One reason Hamas has been a difficult foe for the Israeli military is an extensive network of underground tunnels.

During construction work in a city of central France, archaeologists uncovered a tunnel opening and found a system of ancient Roman passageways. Photos show what remains of the underground structures.

Groundbreaking discovery in Egypt's Sphinx uncovers 'hidden' mystery that fuels theory of underground city. READ MORE: Hall of Records' under pyramid holds key to ancient Egypt's mysteries, say ...

During construction work in a city of central France, archaeologists uncovered a tunnel opening and found a system of ancient Roman passageways. Photos show what remains of the underground structures.

During construction work in a city of central France, archaeologists uncovered a tunnel opening and found a system of ancient Roman passageways. Photos show what remains of the underground structures.

During construction work in a city of central France, archaeologists uncovered a tunnel opening and found a system of ancient Roman passageways. Photos show what remains of the underground structures.

During construction work in a city of central France, archaeologists uncovered a tunnel opening and found a system of ancient Roman passageways. Photos show what remains of the underground structures.

During construction work in a city of central France, archaeologists uncovered a tunnel opening and found a system of ancient Roman passageways. Photos show what remains of the underground structures.