In order to provide a theoretical basis for planning of urban space development which takes into account the factors affecting development of urban space and requirements for aesthetically appealing urban space, Māra Liepa-Zemeša has defined in her PhD Thesis preconditions for perception of urban space and criteria determining its aesthetic quality. The formation of the urban space of Riga is analyzed, assessing the preconditions provided by its geographical location and natural conditions, historical processes of urban development, the society and its demand, as well as laws and regulations. The PhD Thesis has strengthened the role of urban design in the system of spatial planning and analyzed the experience of other countries in formation of urban space and possibilities of its application in Riga.