ABSTRACT The synthesis of arts emerged already in the ancient times – art illustrates a system of aesthetic preferences prevailing in the society of the respective period which is reflected most directly in architecture. Today as well there is a demand for aesthetically appealing architecture of high-quality and for high-quality urban environment in general – there is an ongoing dialogue between architecture and other areas of arts carrying a message that embodies the spirit of the era. The first chapter of the Thesis focuses on development of the synthesis of arts. The synthesis of arts in the 21st century architecture goes beyond the boundaries of classical visual arts, overlapping with the areas of expertise of other branches which are not even art-related. This fact has a great effect on the new identity of architecture – Art Architecture or architecture of arts that is present in the global and also Latvian contemporary architecture. The second chapter of the Thesis deals with the genesis of the image of the building in the process of the synthesis of arts, generating new formal expression patterns in the 21st century. As part of creation of the environment, the synthesis of arts may find its expression in architectural objects of various size, and in urban environment as well. It emerged in the 1960s with unusual and sometimes utopian quests in urban planning aiming to create the urban environment, which would not only be green and harmonious, but also artistic. Such postulates have not become obsolete today and thanks to development of digital technology they continue to evolve. The second chapter analyses the urban space of the 21st century in the context of formal trends. Architecture closely interacts with a human being who observes and evaluates according to his/her subjective perception and artistic taste; therefore it is important and necessary to identify those causes and effects and principles of interaction that determine psycho-emotional perception, looking at these issues through the prism of the synthesis of arts. This aspect has been studied in the third chapter, analysing the interaction models of the informative potential of architecture and psycho-emotional perception from the perspective of the synthesis of arts of the 21st century. It also deals with the role of the synthesis of arts in “architectural treatment”, establishing the role of art synthesis in creation of informative and harmonious spatial environment.