This article discusses how, in an African city - Cape Town - the African Centre for Cities has attempted over the last six years to develop a research method and facility able to respond to a series of pressing problems, by combining methods of scientific research with a deep immersion in the field of urban practices. The article critically explores the assumptions and first results of this experience and then discusses the dialectical tension which binds practices - and the search for increasingly more precise and effective tools for intervention - to the need to bring complex forms of the comprehension of reality into play which, in the conflictual and contradictory context of Cape Town, can only emerge from careful theorisation of the reality.