> Connecting England and France, the Chunnel runs underneath which body of water?And the answer: The English Channel. Short for the Channel Tunnel, the Chunnel runs underneath the narrowest part ofthe English Channel. Both passenger and freight trains use the tunnel, takingjust a half hour to travel the 31.5 miles. The Chunnel is the only fixed linkbetween the island of Great Britain and the European mainland.Photo credit: Denis Charlet / AFP/ Getty Images.Situated between some of themost powerful European nations, the English Channel has long been one of theworld's most important maritime passages. However, rocky shores andunpredictable weather made travel along the Channel challenging and, at times,dangerous. Engineers proposed ideas to bridge the 33-kilometer gap since theearly 1800s, including proposals for artificial islands linked by bridges andsubmerged tubes suspended by floating platforms. Yet it was ultimately the ideaof a long, underwater tunnel – it would be longer than any other in the world – that piqued European interest. Image credit: Kids.Britannica.com.At first, the idea of such a long underwatertunnel seemed impossible. Besides the pressure of the water above, carving adeep passage through solid rock would be incredibly dangerous and expensive forall involved. The project required the invention of the tunnel boring machine, apiece of equipment that had its prototype debut in the creation of the LondonTube System but was not fully developed until 1845. What's more: the UnitedKingdom viewed their geographic isolation as an advantage, fearing the increasedfeasibility of attack from European mainland countries. As such, proposals toconnect the countries were squashed until the late 20th century. With the discovery of a solid layer of rock beneath the English Channel,proposals for the Chunnel gained strength and support. And, since the rise ofair warfare, the argument for UK isolation seemed more and more obsolete. In1985, an agreement was reached. A group of French and British companies investedthe modern-day equivalent of 14 billion pounds in the creation of the underwatertunnel, making it the most expensive infrastructure project of the time. The project called for three tunnels: one to get to France, one to get toEngland, and a smaller service tunnel below them both. In addition, crossoverchambers, air ducts and emergency passages all needed to be built. This amountedto an intended 200 kilometers of tunnels, all in the underwater stretch of 33kilometers. The project ultimately employed over 13,000 workers, and cost thelives of 10 individuals. It was dangerous, uncertain work, but after two and ahalf years of digging, the tunnel was complete – and for the first time sincethe Ice Age, workers reached European mainland on foot. To learn more about this incredible feat of human engineering, check out thevideo below.