The organizers usually focus on an entire country's art, but this year they chose Los Angeles. During its 29-year history, Spain's ARCOmadrid has grown to become not only Europe's largest art fair but also a magnet for the contemporary art world's elite. Every winter, top gallerists, deep-pocketed collectors, museum bigwigs and artists -- not to mention some 200,000 paying visitors -- flock to the Spanish capital for the fair's five-day run.