A great geographical-temporal opportunity exists in Osa peninsula, southern Costa Rica, to drill and instrument a locked segment of the Middle America Subduction Zone, where the plate interface beneath the peninsula is only 4 to 8 km deep. This section of the subduction zone has had large (Mw=7.2-7.4) earthquakes in 1853, 1904, 1941 and 1983. With an average recurrence interval of roughly 40 years, the timing is right to drill, instrument and record data of unrivalled importance before, during and after the next large earthquake in this region. Trench-parallel, landward dipping reverse faults have been mapped on the peninsula, which could represent splay faults and conduits, similar to those imaged offshore Nankai; therefore this will be an ideal site to compare with very important results that are currently obtained in the Nankai Through.  Since the trench is only 20-30 km from the peninsula, submarine cables with seafloor instrumentation, power and data transmission can be deployed and tight to borehole instrumentation, at a much lower cost than in other subduction zones. Drilling and instrumenting the hole would help establish the relationship between geology, upper plate structure, surface deformation and the characteristics of the locked interface. The integration of these datasets would be an opportunity to relate secular processes such as strain accumulation and seismic slip with the longer term evolution of the margin. This will be a chance to contribute to the international efforts done all over the world as part of a network of observatories to understand the genesis of large and destructive earthquakes and contribute to the reduction of their potential damage. The combination of low relative cost and huge scientific potential make the Osa Peninsula a compelling drilling target for the international community. Resources from ICDP and national scientific funding agencies could be leveraged to take advantage of this unique tectonic and temporal opportunity.