There is no city named Simmering located in the State of Vienna region of Austria. Based on the provided source material, "simmering" refers exclusively to a food preparation technique rather than a geographical location.
The term describes a method where foods are cooked in hot liquids maintained at a temperature just below the boiling point and above poaching temperature. To achieve this state, a liquid is brought to a boil before the heat source is reduced to a lower, constant intensity. During this process, the liquid shows little movement without reaching a rolling boil.