A rescue archaeological excavation on the Mendieta area (Sopelana, Biscay province) has shown the presence of lithic industry within an original stratigraphic context of possible Lower Palaeolithic age. The materials containing the lithic industry exhibit stratigraphic and sedimentary features derived from fluvio-alluvial and pedogenic processes. The formation procedures of this open-air site took place under warm and humid palaeoenvironmental climatic conditions, as has been partially confirmed by palynological data. This geoarchaeological characterization supplies important information in order to understand the genesis and location of the scarce open-air archaeological sites of the Lower Palaeolithic age present in the Cantabrian region.