Observatories Augers 68 Cosmic rays 64 Pierre Auger observatory 62 Cosmology 50 Ultra high-energy cosmic rays 26 Extensive air showers 24 Buildings 22 Fluorescence 22 Particle detectors 20 Astroparticle physics 14 Galaxies 14 Large detector systems for particle and astroparticle physics 14 Pierre Auger Observatory 14 Surface detectors 14 Detectors 12 Air showers 10 Charged particles 10 Fluorescence telescopes 10 Geomagnetism 10 Telescopes 10 Anisotropy 8 Astrophysics 8 Atmospheric conditions 8 Calibration 8 Cosmic ray detectors 8 Cosmic ray measurement 8 Geomagnetic fields 8 Neutrons 8 Ultra-high energy cosmic rays 8