The Equator!
As a major global address grid line, the equator divides north from south. So, if you straddle the equator, anywhere on earth, you can have one foot in the northern hemisphere and the other foot in the southern hemisphere.

A line marking the equator, near Quito, Ecuador, known locally as "la mitad del mundo" (the middle of the world).
Global address: latitude 0.0 degrees, longitude 78.45 degrees W