The Channel Tunnel connects the island of Great Britain with mainland France underneath the English Channel. Plans for a tunnel date back to 1802, but it was not until 1984 that British and French leaders agreed to construct it. After six years of construction and $15-21 billion spent, the Channel Tunnel opened in 1994. It is 31 miles long, with 24 miles under water. It connects Folkestone, UK and Coquelles, France, taking 35 minutes to cross. Potential future plans include a second tunnel and further rail integration, but paying off construction debts remains a challenge.