Height profiles of ESO observatories (with extra annotations)

The pristine skies above ESO’s observing sites are perfectly suited to astronomical observations thanks, in part, to the high and dry environments in and near the Chilean Atacama Desert. The Atacama Large Millimeter/submillimeter Array (ALMA), whose observations can be heavily affected by water vapour in the atmosphere, requires the highest elevation site at 5000 metres near the Chilean Andes. ESO’s optical and infrared observatories — at Cerro Paranal, home of the Very Large Telescope (VLT), Cerro Armazones, where the Extremely Large Telescope (ELT) is under construction, and Cerro La Silla — lie at around 3000 metres. These remote sites are far away from the nearest cities, away from sources of light pollution.