Channel Tunnel

The Channel Tunnel , or Chunnel, is a 50.450 km (31.35 mi) long  rail tunnel beneath the English Channel at the Strait of Dover, connecting Folkestone, Kent in the United Kingdom  to Coquelles near Calais in northern France .It was a megaproject with several false starts, but it was finally completed in 1994. It is the second-longest rail tunnel in the world, with the Seikan Tunnel in Japan being longer, but the undersea section of the Channel Tunnel, at 37.9 km (23.55 miles), is the longest undersea tunnel in the world. It is operated by  Eurotunnel. The American Society of Civil Engineers has declared the tunnel to be one of the Seven Wonders of the Modern World.
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Noun
1. the railroad tunnel between France and England under the English Channel
(synonym) chunnel
(hypernym) railroad tunnel