This thesis concerns the monitoring of architectural heritage (e.g. listed monuments and historical buildings) and its transformation during the conservation process, in the context of legal preservation requirements. First the aims and the subject of the work are defined, and current knowledge on the subject is introduced. Then the thesis details problems surrounding the architectural conservation process in practice, particularly concerning the preservation of authenticity, since authenticity is a primary criterion for the nomination and acceptance of sites by the World Heritage Centre. The thesis then presents research which analyses the degree to which the work on monuments in the Banská Štiavnica preservation area has preserved their authenticity, and quantifies authenticity loss which has occurred at certain times; as well as the reasons for its occurrence. The thesis recognises that the process of heritage conservation is one of several factors in authenticity loss. In the interests of objectivity, as well as for the benefit of future field work, an "authenticity test" is proposed. This test has already been applied in specific instances involving monuments in Banská Štiavnica, and has proven effective in pinpointing the reasons for both desirable and undesirable restoration results. The thesis then analyses the components of the conservation process with the aim of identifying the most effective, as far as the influence on final results is concerned. The thesis concludes with a summary of results of the research, and lays out ways in which it may be used to further the theory and practice of cultural heritage preservation and conservation in Slovakia.