Urban planning policies within today’s historic city centers have increasingly leaned toward strict conservation and restoration of the “original image” of buildings. However, this so-called original image is often a collage of multiple periods and transformations, making it difficult to determine a specific era worth preserving. In many cases, this results in interventions being limited to building interiors while preserving the façades, or in the replacement of pavement to pedestrianize streets without altering the original layout. Such an approach contradicts the very historical evolution of cities, where targeted interventions in the past led to significant shifts in urban dynamics across different eras. If this conservative methodology had been consistently applied in earlier times, our historic centers would look very different today. We might not have most of the plazas, Gran Vía might not exist, and depending on where the timeline was frozen, perhaps not even Plaza Mayor. This is not a call for an aggressive “anything goes” policy, but rather for a more open attitude toward change, one that does not reject new proposals outright based on an idealized notion that the past was always better.

In the case of Puerta del Sol, we can trace its formal and functional evolution from a point within the walled city to its current state. It has consistently been a focal point for major urban transformations. What should be preserved here is not a static physical form, but its role as a protagonist in the ongoing evolution of Madrid’s urban fabric and modes of inhabiting the city. Our objective is to fully integrate historic centers—Madrid’s, in this case—into contemporary urban life, addressing current challenges while anticipating future ones. How can these spaces become more participatory, rather than static urban museums curated for tourists? How can they continue to evolve and re-evolve over time? What legacy are we leaving for future generations? Will this be yet another superficial intervention—merely a reconfiguration of flows and paving materials—or a pivotal moment in the historical transformation of the plaza? We propose, as a hypothesis, a future scenario in which Puerta del Sol becomes the neuralgic center not just of historic Madrid but of the entire metropolitan region. A transformation that redefines it from the Puerta del Sol to the Puerta de Madrid and, by extension, to the Puerta de España.