[en] Over the last 30 years or so, a handful of events observed with ground-based cosmic ray detectors seem to have opened a new window in the field of high-energy astro-physics. These Events have energies exceeding 5 x 10¹⁹ eV. They seem to come from no known astro-physical source. Their chemical composition is unknown (or at best uncertain). No conventional acceleration mechanism is considered as being able to explain their production and propagation to earth. Only a dedicated detector can bring in the high-quality and statistically significant data needed to solve this long-lasting puzzle: this is the aim of the Pierre Auger Observatory. While still under construction, the Observatory is already accumulating data. Here we present an overview of the physics results this detector has already provided. (orig.)