"Terrestrial subsurface geomicrobiology is a matter of growing interest on many level. From a fundamental point of view, it seeks to determine wheter life can be sustained in the absence of radiation. From an astrobiological point of view, it is an interesting model for early life on Earth, as well as a representation of life as it could occur in other planetary bodies. Río Tinto is an unusual extreme acidic environment, it rises in the core of the Iberian Pyritic Belt (IPB), one of the biggest sulfidic ore deposits in the world. Today it is clear that the extreme characteristics of Ró Tinto are not due to mining activity, but to the chemolithotrophic microorganisms thriving in the high concentration of metal sulfides of the IPB. To explore the hypothesis that a continuous underground reactor of chemolithotrophic microorganisms thriving in the rich sulfidic minerals of the IPB is responsible for the extreme conditions found in the river, we propose a drilling project to detect the subsurface microbial activity, the potential resources to support these microbial communities, and to follow the in situ geomicrobiological evolution in real time. In this project, we propose to explore the Río Tinto at deep-basement regions (200-1000 m) by means of new approaches comprising: i) detection of life and estimation of the microbial diversity at the drilling sites providing an instant picture of the subsurface habitat, and ii) real time monitoring, inside the borehole, of physico-chemical parameters and biological activity generating essential information to recognize matter and energy fluxes. All these procesess are associated to long-term changes in the underground habitats and are not fully understood based on seasonal discontinuous subsurface analysis. To achieve these goals we will analize cores and fluids in the field site using new and poweful tools."