  Recent measurements of the properties of cosmic rays above 10^17 eV are
summarized and implications on our contemporary understanding of their origin
are discussed. Cosmic rays with energies exceeding 10^20 eV have been measured,
they are the highest-energy particles in the Universe. Particles at highest
energies are expected to be only marginally deflected by magnetic fields and
they should point towards their sources on the sky. Recent results of the
Pierre Auger Observatory have opened a new window to the Universe - astronomy
with ultra high-energy particles.
