Across two very different continents, scientists are mapping vast systems of ancient tunnels that were not carved by rivers or humans. In southern Africa, microscopic passageways etched into solid ...

Tunnels are used to carry traffic through some of the most extreme terrain on the planet and they help ease journeys with reduced travel time. While most tunnels offer a short underground burst of ...

Deep under the Alps, engineers are constructing train lines to connect European countries — and create the world’s longest ...