From one of America's major cities you can drive south under a body of water, and arrive in Canada. Which cities, and which body of water?

It might sound like a riddle, but the unique geography of the Great (Review) Lakes region makes this puzzling trip possible. The Canadian city of Windsor, Ontario, is situated on a peninsula that juts north, placing the bulk of the city directly south of Detroit, Michigan. The two major industrial hubs are separated by the Detroit River, a busy strait that flows south from Lake St. Clair to Lake Erie, forming this unusual section of the international border.

To make the journey, travelers can take the Detroit–Windsor Tunnel. This impressive feat of engineering opened in 1930 and was the first international underwater vehicle tunnel ever constructed. It allows cars and buses to drive for nearly a mile underneath the surface of the Detroit River. This crossing, along with the nearby Ambassador Bridge, is one of the busiest and most economically important border crossings in all of North America.

Historically, this close proximity created a unique dynamic. During the Prohibition era in the United States, the region became a notorious hotspot for alcohol smuggling, with an estimated 75 percent of all illegal liquor entering the U.S. coming through the "Detroit-Windsor Funnel." This history adds another layer to the fascinating relationship between these two cross-border neighbors (Review).