Where: between Folkstone in England and Calais in France

Constructed in just six years, this grand Anglo-French engineering collaboration still includes the longest stretch of underwater tunnel in the world .The English Channel Tunnel is the undersea rail tunnel. It is considered as one among the “Seven Wonders of the Modern World. The length of the channel tunnel is 31.53 miles (50.45 kilometers). The lowest point of this tunnel is 250 feet (75 meters) deep. The undersea part is 23.5 miles (37.9 kilometers) long.