The article analyzed the ideas of the development of mixed-used urban formations. A review of research aimed at developing and forming mixed-used architecture in the urban planning context was carried out. The evolution of the mixed-used space idea, which assumes mixed-using as a phenomenon of the urban environment, was briefly studied, and the prerequisites for forming mixed-used urban formations were analyzed. The interpretations of the concept of the mixed-used complex as one of the types of mixed-used formation were given, and we offered the author's definition of this concept. The advantages of mixed-used urban structures over mono-used ones were outlined, such as adaptability and space flexibility. It is asserted that the development process of a modern city through the creation of mixed-used entities is currently the guarantee of a high-quality urban environment.