The Pyrenean and Cantabrian mountain belts are experiencing renewed attention. The application of new concepts and recent data acquisition have spurred numerous studies and research programs. Lessons from modern hyperextended continental margins have revolutionized the understanding of the orogenic evolution, while recent geophysical surveys are shedding more light into the deep crustal structure. Aspects as the definition of the present-day and past structural style of the former continental margins involved in collision and the nature of plate sutures are being reconsidered. New seismic and gravity modelling are refining the deep structure, addressing lower crust and oceanic subduction. These points will be discussed with the aid of a new series of interpretative crustal transects that integrate the most recent developments in the Pyrenean-Cantabrian orogen.