The article is a presentation of the ethnographic method applied to architecture. The author explains how “slow ethnographers” work when they deal with a building, by focusing on the case of namBa HIPS building by Shin Takamatsu, in Osaka. “Slow” ethnography offers an alternative to “quick theory” intended as a critical theory of architecture that is based on the observation and interpretation of a static object as related to the consolidated spheres of theory and history. Yaneva’s proposal is to start back from the experience of space and objects as built over time: architecture is a process made of cumulative interactions, that unfolds from the design phase to the experience of those who inhabit it, through a continuous intertwinement of human and non-human entities. The study offers itself as a diachronic operation framing the very project as an anticipation of the many velocities to which the project’s transactions are submitted, just as the uses of built space will be: «While working with the speeds, [the architect] does not express or symbolize anything; he simply immerses into the tempo of design and adjusts its different rhythms with engineers, contractors and investors.