Abstract: A rotating blade (1) for a gas turbine comprises an internal cooling structure having at least three cooling air passages (5, 6, 7) in fluid connection with one another by turns (9, 10). An opening (12) provides an outlet for dissolved core material to be removed from the blade following casting of the cooling structure without any residue remaining within. According to the invention, the cooling structure comprises trip strips (13, 15) in the first and second passage (5, 6) with specified ratio of height to distance between trip strips and the trip strips (13) in the first passage being arranged at 90° with respect to the direction of airflow. In a particular embodiment, the trip strips (15) in the second passage (6) are arranged at angle of 45°. The design according to the invention assures sufficient airflow through first and second air passages (5, 6).