The sun was high and the fashion was hot at the Argentine Embassy’s first Heritage Polo Tournament on Saturday. Nearly 500 guests gathered in their polo best for an afternoon of ponies (plus famous Argentine barbecue) at the Summerhill Polo fields in Poolesville, Md.  Academy Award-winning actor Robert Duvall, who owns a horse farm in Virginia, threw the opening ball to much fanfare. The afternoon, which raised money for the Garrahan Hospital in Buenos Aires, ended traditionally with divot stomping and dancing.