Urbanisation combined with climate demographic change will be a challenge for scientists as well as urban planners in order to maintain the quality of life in the cities regarding all concerns. This study helps to improve our ability to simulate the urban climate and evaluates the effectiveness of mitigation strategies. The investigated area is Berlin, Germany, whose urban climate is simulated with the mesoscale urban climate model MUKLIMO 3 developed by the German Meteorological Service, which is a new model which provides an easy implementation of mitigation strategies once it is initialised for a particular city. The work with the model shows that the model needs a time-consuming initialisation phase, but is diversely and widely useful in order to improve the urban climate. The evaluation takes place for 11.07.2010, which was the hottest day in a heat wave that lasted four days and exceeded temperatures of 35 C. The results show that MUKLIMO_3 underestimates the variation in temperature and relative humidity throughout the day as the maximum temperature is underestimated and the minimum temperature is overestimated with mean temperature differences of 4K and 10K at a peak in the night. A comparison with the 1D-simulation of MUKLIMO_3, which gives the boundary conditions, shows better results during the night. Presumably, the 3D-simulation of MUKLIMO_3 does not simulate the outgoing longwave radiation during the night properly. A sensitivity analysis depicted that the differences between the landuse classes (rural and urban areas) is too small, especially during the night. The implementation of high-albedo materials for urban structures and green roofs as mitigation strategies in general show lower temperatures throughout the whole day, while the effect of white scenarios is much higher than green roofs. Mean temperature reductions amount to 0.14K per increase of the albedo of 0.1 for low albedo values, which is relatively low, but still comparable with past research. With a mean cooling effect of 0.2K of green roofs, this mitigation strategy is underestimated compared to other studies. Nevertheless, MUKLIMO_3 shows great promise as a valuable tool for policy-makers and urban developers in order to evaluate the effectiveness of mitigation strategies to improve the micro climate of growing cities regarding the enhanced potential of heat stress.