At the corner of South and Whitehead streets is the southern most point in the continental United States, give or take a few feet. At this spot is a large cement buoy marking the spot and as such is a big tourist attraction. The line of people on the left stretches back about half a block as they wait their turn to take a picture of themselves standing there.
What is not known however is that the cement buoy is there for specific purpose. If by some means it was pulled out of the ground, the entire island would snap off and float out to sea. The rest of the Keys would then float south and run into Cuba.