Here’s an old one that most people probably already know, but I still enjoy it: what is the first foreign country you would reach if you traveled due south from Detroit, Michigan?
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A curve in the Detroit River, the narrow ribbon of water that joins Lake St. Clair to Lake Erie, creates a situation where Windsor, Canada is in fact due south of Detroit. The reason this confounds common conception, of course is that one naturally thinks of Mexico as being south of the United States rather than Canada. Generally this is true but geography doesn’t often follow straight lines. In this instance a river serves as a convenient means to mark an international border and its curvature results in one small portion of Canada that protrudes south of land within the United States.