The northern sector of the Apennines, from the Alps-Apennines knot toward the East, is characterized by E-W trending main thrusts; southeastward, thrust fronts progressively rotate clockwise as far as they reach a N-S trend, typical of the central-southern part of the chain. The E-W trending sector outcrops between Ligurian shoreline, to the south, and Po Plain boundary to the north; under the Po Plain deposits the Apennine front closely approaches the South Alpine frontal thrusts. Field, seismic and well data have been merged in order to reconstruct in 3D the basal surface of the External Ligurian tectonic units in the Northern Apennine sector between the Bobbio window and the Po Plain. From the center of the window this surface becomes deeper in all directions: for instance, moving west, less than 10 km away from the core of the Bobbio window it reaches a maximum depth of thousands of metres below sea level. Using the relationships between the Ligurian complex and its foreland (Po Plain deposits) we are able to trace the emplacement history of the Apennine nappes, dating different phases of tectonic transport from Serravallian to Lower Messinian. The Upper Messinian - Pliocene marks the end of the Ligurian complex transport. Deformation continues outwards: the tectonic structures affecting the Po Plain autochthonous sequences show a mainly Pliocene growth, but locally they remain active during the early part of the Pleistocene.