Recent work in African urbanism conceptualises the African city as a metropolis in flux characterised by interconnected mobilities and heterogeneity, in contrast with the dichotomous construction of public versus private space common in development and planning discourse. Instead, open spaces are not purely private nor merely public but can be understood as liminal spaces, produced through the mobilities and rhythms that are constitutive of this urbanity in flux. A fine-grained study of activities and movements in such liminal urban space in the informal settlement of Jallah Town, Monrovia, Liberia, conducted over the course of two months in 2013, suggests that open spaces in this settlement are both heterogeneous and unstable, traced by fluctuating and porous boundaries between complex spatialities that serve multiple, age- and gender-contingent roles. By incorporating GIS-based spatial analysis with rhythmanalysis informed by phenomenological methods, these spatialities emerge as purposefully developed by residents and central to the reproduction of mobilities, rhythms and social networks constitutive of African urbanism. Such fine-grained analysis, in turn, serves to inform democratic and situated urban design and planning practices, especially in informal communities typically dismissed as irregular and illegal.