The Detroit-Windsor Tunnel is an underwater roadway that connects the cities of Detroit, Michigan in the United States and Windsor, Ontario in Canada. Opened in 1930, it allows vehicles to travel between the two countries, facilitating trade and tourism. The tunnel is approximately 1.6 kilometers (1 mile) long and is a vital transportation link for both regions. The tunnel features two lanes for traffic and is known for its unique design, which includes a curved path. It is one of the busiest border crossings in North America, serving thousands of vehicles daily and contributing to the economic relationship between Canada and the United States.