  The Pierre Auger Observatory, located on a vast, high plain in western
Argentina, is the world's largest cosmic ray observatory. The objectives of the
Observatory are to probe the origin and characteristics of cosmic rays above
$10^{17}$ eV and to study the interactions of these, the most energetic
particles observed in nature. The Auger design features an array of 1660
water-Cherenkov particle detector stations spread over 3000 km$^2$ overlooked
by 24 air fluorescence telescopes. In addition, three high elevation
fluorescence telescopes overlook a 23.5 km$^2$, 61-detector infilled array with
750 m spacing. The Observatory has been in successful operation since
completion in 2008 and has recorded data from an exposure exceeding 40,000
km$^2$ sr yr. This paper describes the design and performance of the detectors,
related subsystems and infrastructure that make up the Auger Observatory.
