The Pierre Auger Observatory

We present the scientific motivation, conceptual design and status of the P. Auger Observatory, a hybrid detector designed to measure both the longitudinal and the lateral profile of giant air-showers produced by cosmic-rays of energy above 1019 eV. Two ground arrays of water Cerenkov tanks overlooked by fluorescence detectors will cover an area of 3000 km2 each. They will be build in the Southern and Northern hemisphere to provide full sky coverage. The total aperture of 14000 km2sr will allow to study all observable aspects of cosmic rays from below 10 EeV up to arbitrarily high energies with an unprecedented accuracy