While deserts are by definition, places where rain is scarce, there is only one area on this earth - the central portion of Chile's Atacama Desert, where it never ever rained - at least since humans started keeping a record - about 400 years ago!
The most amazing part is, that this 600-mile stretch of land lies right alongside Chile's coast, next to the biggest body of water on Earth - The Pacific Ocean. Though drier than all other deserts, the temperature in the Atacama Desert is quite cool, ranging from 0-25 degrees Celsius, thanks to its high altitude.
The reason for the extremely arid weather is its location, in the rain shadow, smack between the Andes mountains and the Chilean Coast Range. The warm tropical air that brings rain to the South American rainforests are prevented from coming across thanks to the high Andes - Instead, the high altitude forces the air to cool and precipitate right on the mountains. By the time it rolls on the other side the warm air holds on to whatever moisture it has, instead of falling on the ground below.
While the weather makes it almost impossible for anything to survive, the area's unusual landscape has made it a goldmine for scientists and astronomers.
The arid cold weather is the closest substitute for the weather on Mar's giving NASA scientists the perfect testing grounds for any equipment they wish to send to the Red Planet.
Also, thanks to the high altitude, nearly non-existent cloud cover, dry air, lack of light pollution and radio interferences from cities, the area is perfect for astronomy observations.
Already home to two major European observatories, a third dubbed ALMA, a collaboration between Europe, Japan, United States and South America is currently underway. As would be expected, the area is also popular among filmmakers looking to film scenes on 'Mars'. However, while the Atacama Desert maybe the 'driest' desert in the World, it is only the second driest region - the winner? Icy Antarctica!
sources: geography.about.com, wikipedia.org,www.extremescience.com