English: This Picture of the Week shows the grand skies of the Chajnantor plateau in the Chilean Atacama desert. The rare sight of clouds in this typically dry and arid region creates a dramatic display of reds and blues, as well as a sun pillar –– an optical phenomenon caused by ice crystals in the atmosphere –– that emanates from the Sun in line with a telescope. This large antenna is a part of the Atacama Large Millimeter/submillimeter Array (ALMA), which is co-owned by ESO.ALMA is one of the most powerful observatories in the world for radio astronomy. Its collection of 66 antennae — like the one pictured above — has been responsible for many incredible ground-breaking discoveries, including contributing to the creation of the first image of a black hole.