Abstract A non-conventional wind tunnel for low-speed applications in both Aeronautical and Wind Engineering fields has been designed at Politecnico di Milano, as a joint research of the Mechanical and the Aerospace Departments. Peculiarity of the facility is the contemporary presence of two test sections having very different performances, the first one characterised by higher speed and low turbulence, the second allowing ground boundary layer simulations at lower speed and wider test section size. Very strict size constraints of the building in which the wind tunnel must fit made the fulfilment of the general specifications a difficult task and led to the adoption of nonconventional solutions in the wind tunnel layout and specific components design. The paper presents the design criteria that supported the choice of the original solution and discusses the feasibility of the plant on the basis of experimental analysis on a 1 : 9 scale model.