Urban development is often characterized by changes introduced in land use, which are followed by the evolution of complex spatial structures in metropolitan areas. These distinctive urban features influence the microclimate by altering the total energy balance of the city and often implicate higher temperatures due to heat storage in urban areas (Nunez and Oke 1977, Grimmond et al. 1999). This circumstance, referred to as the urban heat island (UHI) phenomenon (Oke 1982), has been the focus of a number of studies (e.g. Giridharan et al. 2004, Unger 2004). The urban climate is affected by a variety of influences such as geometry and vegetation (Memon et al. 2008, Santamouris 2007). Increase in average temperatures has far-reaching implications for issues such as thermal comfort (heat stress), mortality, energy consumption and urban planning (Taha 1997, Lee and Park 2008). In this context, this paper presents a systematic framework for the assessment of microclimatic conditions in large-scale spaces. Various geometric properties and topological relationships are used to calculate microclimatic attributes for five representative areas in Vienna.