ABSTRACT This study examines Tianqiao, the largest commercial and entertainment centre, which underwent a significant transformation into the most popular public space in Republican Beijing. Spatial informality has often been overlooked in planning history, due to its deviation from traditional disciplinary norms, tools, and materials, yet it can offer valuable insights into Chinese urban public spaces and their social values. Drawing on a wide range of sources, including government documents, newspapers, social surveys, and personal records, this paper elucidates how everyday life and popular culture emerged as effective strategies for the poor population to exert their political power and passively resist the state's incomplete urban regularization efforts. This exemplifies a distinct type of Chinese public space that acts as a mediator between the state and society, particularly from a bottom-up perspective of urban modernization.