This paper aims to study the feasibility of building an Earth-skimming cosmic tau neutrinos detector, with the aim of eventually identifying the ideal dimensions of a natural site (mountainvalley) for the detection, with the energy range to be determined (evidently, the highest possible numbers range from 1015 eV to 1020 eV), and possibly locate one such site in Algeria. First, a Monte Carlo simulation of the neutrino-[mountain]matter interaction as well as the resulting decay of the tau lepton is conducted to determine the optimal dimensions of the mountain as well as the location of the tau decay in the valley. Second, a CORSIKA (COsmic Ray Simulation for KAscade) simulation with the CONEX option is conducted to track the evolution of the almost horizontal air shower born from the tau lepton. Among the particles produced in the shower are: electrons, muons, gammas, pions, etc). The study of the spatial distribution of muons enables the discovery of the optimal width of the valley, and consequently, the distance at which to lay the detection network.