In the period between the two world wars, the latent tensions between the European nations resulted in the construction of defensive positions on the borderlines of major European countries. Under the same conditions, the Italian Kingdom built an extensive fortification line, i.e. the Alpine Wall. The Kingdom of Serbs, Croats, and Slovenes (SHS) replied to it with the Rupnik Line. On the base of the Treaty of Rapallo, a 289-km long demarcation line was built with an exceptional defence infrastructure, which interfered with vast natural areas of exceptional quality that are protected by various nature conservation regimes today. The research presented in this paper is focused on a specific land expropriation. The goal is to understand the historical perspectives and assess the current significance of this fortification system with its impact on the natural environment. The system of spatial assessment of the architectural, urban, regional and spatial planning aspects and landscape interpretation has been developed with the use of spatial planning mapping and other methods. It was tested on the case study of the Žiri Municipality to establish a possible systemic base on which the entirety of the Rapallo border with its defence infrastructures could be mapped and their contemporary role assessed.