Historical cities as an object of protection: approaches to the preservation of urban planning heritage in Russia

. The historical city is one of the most complex objects of research, being a “living” organism, the environment of modern man, a combination of natural and man-made, tangible and intangible elements. The relevance of the study of the historical and urban planning environment is caused by the ongoing search for the most effective approaches to preserving the heritage of cities and the sustainable development of their territories. Systematic and structural analysis of such a phenomenon as a historical city, identification of internal relationships of elements that make up the historical and urban planning environment; comparison of existing tools for the protection of urban planning heritage and determination of the most effective mechanism for its preservation, proposed by modern Russian legislation. Based on the analysis of existing tools for the protection of the historical urban planning environment, the authors propose to consider the procedure for determining the boundaries and subject of protection of historical settlements as one of the aspects of the implementation of the international approach to the preservation of historic urban landscapes (HUL approach), and identify ways to improve the national tools in the field of urban planning heritage protection.


Introduction
Modern understanding of the historical city goes far beyond its interpretation as a simple set of objectively existing elements -planning structure, development and formed compositional connections. Today, the historical city is a combination of natural and man-made, tangible and intangible elements. It is a "living", constantly changing organism that transforms along with the changes inherent in human society: the development of social needs inevitably leads to the need to adapt the physical matter of the city [1].
As dynamic structures, historical cities turn out to be one of the most complex objects of research, and their preservation and development is perhaps the greatest challenge of our time.
Despite the considerable study of the topic in both foreign and domestic scientific literature, the Russian practice has not yet formed a legal tool that can ensure the comprehensive preservation and development of historical urbanized territories, which will take into account the complex internal relationships between the elements that determine the image of the city and its identity.
Historical cities have long been in the field of view of specialists. At the same time, their selection as an independent object of research and protection took place gradually, in parallel with the formation of ideas about the value of various elements of the urban environment and the awareness of the need to preserve them [2][3][4]. With the development of the international system for the protection of cultural and natural heritage, more and more attention has been paid to the comprehensive preservation of the human environment [1,[5][6][7], urban territories development [8][9][10] and problems of urban planning regulation [11][12][13][14][15]. An important area of research has also been the development of approaches to the study and analysis of the practice of preserving the historical urban environment and its individual components [16][17][18][19][20][21][22]. The expansion of the spectrum of problems of urban conservation has forced theorists and practitioners of heritage protection to discuss the question of the fundamental possibility of preserving historical cities, taking into account their changing nature [1,23].
As a result of a long study of the urban planning heritage and the accumulation of significant experience in the field of its preservation, the idea of the historical city as a special object of protection was formed. As a result of the stratification of cultural and other values, it also includes a broader context formed by natural and man-made elements [24]. One of the foundations of the approach developed by the international community to the preservation of such an object was the recognition of the feasibility of spatial transformation of the urban territory, which made the management of changes one of the most urgent tasks.
In the context of accelerated urbanization processes, which often provoke social tension, the definition of approaches and detailed elaboration of national tools that will ensure the preservation and sustainable development of the historical and urban planning environment are extremely relevant.

Methods
Within the framework of this research, the historical city was considered as a system that includes a certain set of elements of both material and non-material order, united by historically formed internal connections. The components of this system include not only city-forming elements such as planning structure, development and visual relations, but also "aspects of social and cultural practices and values" [24]. The object of the system and structural analysis was also a set of measures provided for by the current Russian legislation in the field of state protection of urban planning heritage. The results of the analysis and comparison of existing legal instruments became the basis for the conclusion about the most effective mechanism for preserving historical urban territories and possible ways to improve it.

Research results and discussion
The historical urban environment can be defined as a system formed by several components. Two of them -the planning structure and development -are universal elements that form the structure of any city. The third component -the natural landscape -is used as a framework for the implementation and development of urban planning ideas. And, finally, a person with his ability to objective or subjective -emotionally colored or associatively conditionedperception becomes a key link in the formation of a system of visual connections and the perceived image of the city. The landscape and planning structure among all components are the most stable (with the exception of periods of major urban planning transformations). Development is the most materialized component of the urban matter. It is of paramount importance for maintaining the valuable qualities of the environment and is extremely vulnerable to various changes [25]. Man has a special role in this system. It is both a part of the environment, a keeper of ideas about its value, and an external observer. Therefore, the image of the city -is largely a product of human consciousness: material elements serve as signs of urban structures, ideas, images, symbols that together make up a complete mental picture [26].
The particular importance for the formation of the visual image of the city is the silhouette, which is a carrier of information about the development and layout of the city, the natural relief, the features of urban planning composition [16]. The content of the silhouette is read by a person in the process of perception of panoramic and perspective views of the urban landscape [26]. Awareness of the intangible value of urban space is associated with understanding the general cultural context, which is expressed by the silhouette and composition, as well as individual architectural objects.
As a result, the image of the city turns out to be the sum of the material and intangible: visible by person elements are supplemented by associations with events and phenomena. And visual connections that unite the material components of space are born due to the presence of an observer -according to the figurative expression of M. W. Hungerford, "beauty is in the eyes of the beholder" [27]. This makes it possible to say that ultimately the preservation of the city -is the preservation of the image perceived by a person. In this context, the material objects that form the environment become proof of its stability and authenticity, attributes of its value, and the speed and direction of transformation must be socially justified and commensurate with the "content" of the environment itself. In this regard, an important aspect is the preservation of spatial and semantic landmarks that provide recognition -one of the foundations of cultural identity. And, consequently, "the natural trend of urban growth should not be stopped without any consideration, but only limited in such a way that it takes the safest and most profitable direction for the city" [23].
The changeability and dynamic character of historical cities is an axiom for almost everyone today. The long way passed by experts in the field of urban planning heritage protection has led to an understanding of the need to manage the changes that the city undergoes in the process of development of the territory and society. As a result, the regulation of spatial transformation is considered one of the signs of sustainable development [25].
The tools for protecting the historical and urban planning environment, introduced by Russian legislation, have significantly expanded over the past decade. One of the most common and traditional tools is protection zoning, which involves preserving the historical environment of cultural heritage objects. At the same time, the environment parameters that will allow preserving the monument and its valuable characteristics (subject of protection) are maintained. Given that the boundaries of protection zones can cover quite large territories (for example, in the case of establishing joint protection zones), this tool could become the basis for comprehensive preservation of the historical and urban planning environment. However, in practice, the establishment of protective zones led to "isolation of significant areas of cities from life processes" [28].
In 2012 in connection with the revitalization of the inclusion of cities in the list of historical settlements has been expanded and detailed requirements for the protection of urban areas, the composition of the subject of protection of historical settlement, which includes historically valuable city-forming objects (buildings and structures), planning and spatial structure, composition, and silhouette of the development, the ratio between different urban spaces, composite-species communication (panoramas) and the ratio of natural and man-made environment, i.e. those elements that, as shown above, form the perceived image of the city. Giving the territory the status of a historical settlement implies the preservation of all the material components of the historical and urban planning environment as an expression of the uniqueness of the human settlement.
In 2014, amendments were made to Federal law No 73-FZ of 25.06.2002 "On cultural heritage properties (historical and cultural monuments) of the peoples of the Russian Federation" in terms of defining the features of state protection of places of interest: attributing the centers of historical settlements or fragments of urban planning and development to places of interest provides a basis for preserving the components of the historical and urban planning environment as part of the subject of protection. At the same time, restrictions imposed on the territory of a place of interest are aimed at preserving those elements of the environment that are an expression of the value of a particular place of interest.
Thus, it seems that today the most effective tool for providing comprehensive protection of the material components of the urban environment is the historical settlement.
The concept of "historic urban landscape" (hereinafter -HUL), which has become the result of many years of research by the international expert community, is the closest in content, but, nevertheless, much more elaborated and multi-layered. The 2011 recommendation [24,29] established the concept of HUL, which is interpreted not only as a new way of understanding historical urban territories, but also as an integrated approach to their conservation. HUL pushes the boundaries of the usual idea of the value of the historical environment. Not limited to physical parameters, HUL also takes into account intangible components that determine the identity of the city and are one of the foundations of the cultural identity of its residents. Thus, the HUL approach is the basis for including activities aimed at preserving the historical city in the overall context of sustainable development. This is made possible by the use of a number of tools adapted to a specific cultural environment [30].
Despite the significant similarity of the two concepts, the significant difference between HUL and the historical settlement is that the first recognizes the socio-cultural and economic aspects as part of a broad urban context. Therefore, today, according to the international community, the main goal of preserving heritage is not so much to preserve objects, but to maintain and develop the values that they embody. In this regard, value characteristics become the basis for choosing a strategy for heritage preservation based on a value-based approach.
When analyzing the historical settlement as a tool, attention is drawn to the insignificant elaboration of the mechanisms laid down in it for preserving certain components of the historical and urban planning environment. Despite the declared transition from object protection to environmental protection, regulatory regulation still affects only certain environmental parameters that are not considered in a complex, and does not take into account the internal connections between the individual components of the perceived image of the city. The very content of the concept of "preservation" in the structure of prohibitions and restrictions is quite general and is not disclosed in relation to specific elements of the historical environment.
One of the most striking examples can be Saint-Petersburg -a city that has the status of a world heritage site due to the exceptional integrity of the historical and urban planning environment, based, among other things, on the unique characteristics of the natural landscape. Saint-Petersburg also has the largest number of cultural heritage properties in Russia. When we talk about the integrity of the environment, we primarily mean visual integrity, since the physical aspect of the authenticity and integrity of the environment is the basis for a person's perception of the integral image of the city. The method of protecting the visual integrity of the historical environment is the requirement to preserve historical buildings and structures, high-rise regulation of the parameters of reconstruction and new construction. However, the complex of measures to protect the historical environment of cultural heritage properties on the territory of Saint-Petersburg does not exclude the possibility of reconstruction of historical buildings with changes in size and appearance, as well as the construction of new buildings and structures within the maximum allowed height restrictions. As a result, in the existing panoramas of the Neva water area -the main planning and compositional axis of Saint-Petersburg -include new buildings erected in violation of the historical compositional principles of forming river panoramas. The facades of new buildings are not related to historical ones by the architectural module, outline of the lines of crowning cornices and roofs. These features negatively affect the integrity and compositional completeness of river panoramas, the silhouette and ultimately the perceived image of the historic center.

Conclusions
Due to the accelerated pace of urbanization, historical cities are still at the peak of research interest, and discussions about ways to preserve and develop urban territories do not lose their relevance.
As a result of the analysis of the parameters and components of the historical and urban planning environment, it seems reasonable to conclude that the key role of the image perceived by a person in the process of preserving the city's identity. Thus, the main object of protection should not be individual elements, but the visual integrity of the urban environment.
The HUL approach proposed by the international expert community, introducing a more comprehensive definition of urban territories into the practice of heritage protection, requires detailing and adaptation to a specific cultural context. Historical settlement as a tool for protecting urban planning heritage can be considered as one of the aspects of this approach. At the same time, it should be noted that the mechanisms for the protection of historical settlements established by current Russian legislation require detailed and mutual coordination. This will allow us to move from the paradigm of isolated protection of individual environmental parameters to the paradigm of its comprehensive conservation.