Clubs, literary cafés, theatres, cinemas, bank halls, courtrooms, museums, libraries, and commercial galleries constructed the emerging public sphere of the city of Santiago de Chile in early twentieth century. These interiors triggered a process of transformation and redefinition of the public sphere that mirrored an increasing complexity of the Chilean state and society. Functioning as a synecdoche, they encapsulate and map the relationships with the city outside. Analogous to publication The Microcosm of London published in 1808, this essay proposes to read Santiago as a microcosm –a hundred years later. A series of rooms established a network of carefully designed interiors whose importance relies –then and today– as much on their material condition, as in the social activities and relevant decisions that were taken in them. By classifying them in three categories: (i) circles as rooms that primarily served functions of sociability; (ii) institutions as places for the administration of state power; (iii) cabinets designed to store and/or display objects, the interiors are taken as mediators between objects and subjects. The stories of these rooms not only narrate their past relevance but also projects their status in the public sphere of Santiago.