Urban heat island and heat waves are major environmental hazard in cities, consequence of the rapidly increasing global warming and the uncontrolled urban sprawl. Green technologies and nature-based solutions are gaining interest because of their capability to reduce the urban ambient temperature and to provide cooling shelter for human beings. This paper aims at quantifying the impact of nature-based solutions by creating a virtual small urban park in a square localized in the eastern quadrant of Rome, Italy, an area deeply affected by urban overheating. The study starts from a previous paper in which an atmospheric model was implemented and validated against ground measurements, next used to assess the impact of different heat mitigation technologies. In this paper, the validated model has been further parametrized for the vegetation component, by using species-specific literature data and in-situ ecophysiological measurements, and used to analyse the benefits of tree planting. Several scenarios have been implemented, taking into account the cooling benefits of different tree species, characterized by contrasting leaf functional trait, as well as different tree size. Atmospheric simulations are run for the reference case and for the “green” scenarios for selected days of July 2023. Key-performance indicators of the analysis are the ambient temperature, the wind speed and the physiological equivalent temperature (PET), a well-known index for the assessment of thermal comfort, stress and biometeorology. The change of such parameters in the different scenarios allows to quantify the impact of greenery on the improvement of the liveability and the thermal quality of urban spaces.