Abstract Mountains and highlands are not what scholars have conventionally imagined them to be: environments that limit and constrain their inhabitants in deterministic ways. Rather, mountains and highlands provide unique opportunities for people to engage in creative transformation of their societies. Highland communities are connected to a wider world, and they radically remake and experiment with their landscapes, settlements, and societies. Mountains serve as birthplaces and testing grounds for statecraft, urbanism, irrigation, and monumental landscape engineering. Here we explore the diversity of highland communities by analysing the latest archaeological and historical discoveries from three regions across Southeast Asia: the Kulen mountains (Cambodia), the volcanoes of central Java (Indonesia), and the Ifugao highlands (the Philippines). We find that, far from being a negative image of the ‘civilized’ lowlands, mountains were creative, diverse, dynamic, and well-connected places. This compels us to change the way we conceive of today’s highland communities and their relationships to modern nation-states.