Abstract Stage I of the enlargement of Atocha Railway Station aimed primarily to adapt the facility to a new operating model, raising the station's capacity essentially by separating arriving and departing passenger traffic. This article describes the project background, scope and justification, as well as the main structural members and most significant works involved in the enlargement, distinguishing between construction in platforms and tracks and existing facility restructuring. In light of the complex geometry of the new roofs over Atocha Station, computational fluid dynamics (CFD) techniques were deployed to verify the pressure coefficients initially adopted for the new platform canopies by extrapolation from the existing legislation. The structural engineering involved is addressed. Lastly, logistics and planning are discussed, with an account of all the possible scenarios and the challenge of performing many activities simultaneously on a tight schedule in limited quarters (power outages, track beds, high voltage works,…). The exceptional constraints inherent in the need to maintain high-speed train (“AVE”) service during the works intensified the overall complexity.