A gas turbine including an inner casing and a rotor having rotatable blades with a shroud and a fin, and a cooling arrangement arranged in a cavity in the casing and about the rotatable blade. The blade shroud includes a protrusion extending away from the blade leading edge into the cavity and openings in the cavity wall for a cooling fluid. The protrusion is defined by angles in relation to the flow channel wall. The protrusion affects a vortex flow of cooling fluid entering through the openings and a vortex flow of hot gas entering from the flow channel into the cavity. The double-vortex formation reduces a mixing of the cooling flow with the hot gas flow and increases the efficiency of the cooling arrangement of the blade shroud and cavity walls.