Deserts, tropical forests, high mountains, and polar areas, have shaped the history of science. They serve not only as sites for field research and expeditions but also as territories where imperialist States have erected specialised infrastructures to facilitate scientific work and human habitation. Three scientific sites are compared: a volcanological and seismological observatory, a rocket launch base, and a biological station, each located in different French overseas territories. The article inquires how the development of these remote scientific infrastructures reflected common patterns that transcend historical epochs and decolonisation processes. This historical and comparative approach, makes it possible to conceptualise a new `place as institution,' `scientific outposts' that bridge the history of colonial sciences with postcolonial STS. Specifically, three (post)colonial processes are scrutinised and combined: the establishment of scientific infrastructure, the dynamics of centre-periphery relations within sciences, and the engagement with local populations - a set of processes we term `(post)colonial placing.' This conceptual framework enables a fresh perspective on STS spatial concepts such as the `truth spot' as well as relations between `field stations' and `calculations centers,' linking them with postcolonial scientific practices as epistemological and material `boundary work.' Postcolonial placing gives rise to `scientific outposts,' distinct from laboratories and field camps. Their analysis links an geopolitical imperial perspective with concrete infrastructures, highlighting continuity beyond formal decolonisation processes. A comprehensive definition of scientific outposts finally grounds these places in the interconnection of five criteria referring to their: materiality, geography, politics, sociability, and epistemology.