Unsteady three-dimensional flow phenomena have major effects on the aerodynamic performance of, and heat transfer to, gas-turbine blading. Investigation of the mechanisms associated with these phenomena requires an experimental facility that is capable of simulating a gas turbine, but at lower levels of temperature and pressure to allow conventional measurement techniques. This thesis reports on the design, development and commissioning of a new experimental facility that models these unsteady three-dimensional flow phenomena. The new facility, which consists of a 62%-size, high-pressure gas-turbine stage mounted in a transient wind tunnel, simulates the turbine design point of a full-stage turbine. The thesis describes the aerodynamic and mechanical design of the new facility, a rigorous stress analysis of the facility’s rotating system and the three-stage commissioning of the facility. The thesis concludes with an assessment of the turbine stage performance.