A gas turbine engine includes a propulsor, a compressor comprising a compressor rotor, and a turbine comprising a turbine rotor fixedly mechanically coupled to the compressor rotor. The propulsor and the compressor are arranged in axial flow series. The turbine rotor is radially outward of the compressor rotor, and the direction of fluid flow through the turbine is generally opposite the direction of gas flow through the propulsor and the compressor.