Power plant comprising a gas turbine assembly; the gas turbine comprises: - a compressor configured for compressing incoming air and feeding compressed air to a plenum; - a combustor assembly configured for feeding at least a fuel coming from a fuel source in the compressed air and for generating by combustion a hot gas flow; - a turbine configured for being driven by the hot gas for performing work on a rotor connected to a generator; - a heating assembly comprising a heating device configured for pre-heating the fuel, an inlet fuel duct connecting the fuel source to the heating device, an outer fuel duct connecting the heating device to the combustor assembly, an inlet heating medium duct for feeding a heating medium to the heating device and a outlet heating medium duct for delivery the heating medium from the heating device; - a cooling assembly comprising a cooling device configured for cooling spilled high pressure air, an inlet air duct connecting the plenum to the cooling device, an outlet air duct connecting the cooling device to the turbine and/or the rotor for cooling reason, an inlet cooling medium duct for feeding a cooling medium to the cooling device and an outlet cooling medium duct for delivering the cooling medium from the cooling device; wherein the inlet heating medium duct is connected to the outlet cooling medium duct so that the cooling medium delivered by the cooling device is used as heating medium in the heating device for pre-heating the fuel; wherein the power plant comprises a steam turbine assembly wherein the exhaust hot gas leaving the gas turbine is used as heating medium for heating the water/steam circulating in the steam turbine assembly; characterized in that the inlet cooling medium duct is connected to the steam turbine assembly for feeding to the cooling device steam spilled from the steam turbine assembly. - a compressor configured for compressing incoming air and feeding compressed air to a plenum; - a combustor assembly configured for feeding at least a fuel coming from a fuel source in the compressed air and for generating by combustion a hot gas flow; - a turbine configured for being driven by the hot gas for performing work on a rotor connected to a generator; - a heating assembly comprising a heating device configured for pre-heating the fuel, an inlet fuel duct connecting the fuel source to the heating device, an outer fuel duct connecting the heating device to the combustor assembly, an inlet heating medium duct for feeding a heating medium to the heating device and a outlet heating medium duct for delivery the heating medium from the heating device; - a cooling assembly comprising a cooling device configured for cooling spilled high pressure air, an inlet air duct connecting the plenum to the cooling device, an outlet air duct connecting the cooling device to the turbine and/or the rotor for cooling reason, an inlet cooling medium duct for feeding a cooling medium to the cooling device and an outlet cooling medium duct for delivering the cooling medium from the cooling device; the inlet heating medium duct is connected to the outlet cooling medium duct so that the cooling medium delivered by the cooling device is used as heating medium in the heating device for pre-heating the fuel; wherein the power plant comprises a steam turbine assembly wherein the exhaust hot gas leaving the gas turbine is used as heating medium for heating the water/steam circulating in the steam turbine assembly; characterized in that the inlet cooling medium duct is connected to the steam turbine assembly for feeding to the cooling device steam spilled from the steam turbine assembly.