Underground matters, redefining public spaces through underground space use: insights from Paris and Barcelona

The interconnection between urban development and underground space has been a recurrent theme throughout history. The use of underground space has consistently played a role in the evolution of cities, with underground networks and services increasingly pivotal in meeting citizens’ diverse needs. Global challenges, particularly health and environmental crises, have prompted a revaluation of urban priorities, especially in dense European cities where underground infrastructure contributes meaningfully to strategic planning. Using Barcelona and Paris as examples, this article explores why the underground is crucial to addressing three major challenges that dense European cities face as they work towards a climate-resilient future: enhancing liveability in public spaces, regenerating established urban areas, and fostering sustainable mobility.