They fly through the air with the greatest of ease, and we can’t look away: beginning on February 25, Ringling Brothers and Barnum & Bailey bring their “Legends” to Brooklyn’s Barclays Center, featuring both performers (acrobats and clowns) and creatures (unicorns and wooly mammoths) of legend. The food concourse will be transformed into a family-friendly feast, with grilled cheese and PB & J replacing the usual concession fare.