The two countries that share the most extended border in the world are Canada and the United States. This border stretches approximately 8,891 kilometers (5,525 miles), making it the longest international land border globally. It traverses various terrains, including mountains, forests, and lakes, and encompasses numerous border crossings. The Canada-U.S. border is significant for trade, tourism, and diplomacy between the two nations. Several major cities, such as Detroit and Toronto, are located near the border, facilitating cultural exchange and economic cooperation.