A multidisciplinary study has been carried out in Hontomín (Spain) to determine the basement structural setting, its geometry and that of the sedimentary succession of an area aimed to be the first Spanish pilot plant for CO2 storage. An integration of coincident 3D seismic results, borehole data and unpublished microgravity data was used to reproduce the deep structure and topography of the basement and to quantify the thickness of the Triassic Keuper evaporites. The subsurface structure is characterized by a half-graben setting filled with Keuper evaporites (up to 2000 m thick) forming an extensional forced fold. All datasets clearly identify two main fault systems compartmentalizing the main structural domain into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome.