The Channel Tunnel is a 50.5 km railway tunnel under the English Channel that links France and the United Kingdom. It has the longest underwater section of any tunnel in the world at 39 km and an average depth of 40 meters. The tunnel allows the Eurostar high-speed train to travel between London and Paris in 2 hours and 20 minutes, and between London and Brussels in 1 hour and 57 minutes. It provides an important transport link for passengers, trucks, cars, and motorbikes while avoiding weather delays that can impact travel by ferry or ship.