In the present paper a computational methodology for assessing and improving the microclimate in the urban environment is developed. A Computational Fluid Dynamics (CFD) model is described, which accounts for the evaporation occurring on water surfaces as well as the evapotranspiration from plant surfaces and tree foliage. Solar radiation and wind effects are also taken into account. Additionally, thermal comfort indices are implemented in the model, hence local information is provided regarding thermal sensations (bioclimatic maps). Surface temperature and air temperature at pedestrian level, are also used to characterize the microclimate. The methodology is demonstrated by means of a case study, which refers to the area of Gazi in Greece. Initially, the model is applied for simulating the airflow pattern throughout the domain of interest. The numerical results reveal the problematic areas in terms of thermal discomfort and wind effects. Based on that information advanced bioclimatic techniques are suggested to reduce severe heat stresses and to eliminate these areas. The effectiveness of the architectural interventions is tested by estimating the microclimate-indices differences compared to the existing conditions. It is concluded that the proposed methodology serves adequately for applying effective bioclimatic strategies to mitigate the Urban Heat Island (UHI) effect