Every December the center of the art world convenes not in New York, Tokyo, or London, but in a town known more for its wide sandy beaches, café Cubano, and conga rhythms. Art Basel Miami Beach, which wraps up its three-day run today, is the American leg of an international art fair also staged in Basel, Switzerland (where the festival started in 1970), Hong Kong, and Paris. The event, now 20 years old, is the most comprehensive contemporary art fair in North America, attracting thousands of artists, dealers, collectors, appreciators, and just fun-seeking tourists for this annual burst of creativity steps from the sand.