A rotary drying cylinder (1) for plants for the production of bituminous macadams, extending along a main axis (2). The drying cylinder (1) comprises a burner (7), connected to the cylinder, which generates a flame (9) that extends inside the cylinder (1). The drying cylinder (1) internally comprises a tube-shaped shielding structure (10) having an axis of extension which is substantially parallel with the main axis (2) and extending from the burner (7) so that, in practice, the flame (9) is at least mainly confined within the shielding structure (10), there thus being a separating ring (12) between the shielding structure (10) and the inner surface (13) of the drying cylinder (1). The shielding structure (10) comprises a plurality of hollows (17) facing towards the inner surface (13) of the drying cylinder (1) for containing, in practice, the material being dried. The shielding structure (10) is at least mainly made of heat conducting materials.