What is the future of peripheral landscapes and radically depopulating mountainous regions and how do we, as architects and urban researchers, address the challenges of those regions? The dissertation shifts the focus of urban research beyond the traditional city boundaries and aims to explore processes of urbanisation that occur at peripheral landscapes, seemingly intact areas of nature and uninhabited land in order to expose their forces and address their implications. In particular, the research revisits the mythicised landscapes of Arcadia in Greece, framing a contemporary, radically depopulating mountainous region at the southern outpost of the Balkan peninsula. Under the overarching hypothesis that “peripherilisation” is a process of urban transformation, the dissertation seeks to i) critically investigate the formation of a peripheral landscape in relation to a broader historical, political and geographic context, ii) identify and map emerging urban patterns and novel urban typologies, detecting their socio-ecological implications and their latent potential, iii) employ the research findings as a basis for the formulation of alternative strategies and future visions for design and governance of the mountainous regions. The dissertation is embedded in the research tradition, initiated by ETH Studio Basel and further developed at the ETH D-ARCH the last twenty years. It has at its core the territorial approach, linking the social, political and cultural aspects of urbanisation to transformations in land structures, land-use patterns, and ecological networks. In particular, the dissertation will use the theoretical ground of critical urban theory and the concept of extended urbanisation, further introducing an ecological perspective, novel for urban analysis of socio spatial processes occurring at peripheral landscapes. It will frame four distinct socio ecological configurations, present at the mountainous region of Arcadia and study them via four corresponding case-studies, through qualitative exploratory field-work and synthetic cartographic representation. The dissertation contributes to the scarcely explored field of urban analysis of peripheral landscapes and mountainous regions, elaborating visions and future strategies in design and governance.