The Atacama Desert is a 40,000 square mile plateau in Chile. Its altitude varies, but 7,000 feet is common and mountains on it reach above 22,000 feet.
It is clear and dry with an average of 30 cloudy days per year, and an average annual rainfall of about a millimeter.
Observatories and telescopes include:
La Silla Observatory is at the edge of the desert. Plans and under construction:
Atacama Cosmology Telescope (ACT)
Atacama Large Millimeter Array (ALMA)
Atacama Pathfinder Experiment (APEX)
Atacama Submillimeter Telescope Experiment (ASTE)
CMB Stage-4 (CMB-S4)
Cherenkov Telescope Array (CTA)
European Extremely Large Telescope (E-ELT)
European Southern Observatory Very Large Telescope (ESO VLT)