Portal:Astronomy/Picture/22 August 2005
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![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Olympus_Mons_caldera.jpg/300px-Olympus_Mons_caldera.jpg)
Olympus Mons is the largest volcano in the Solar System, rising some 27 km above the Tharsis plain on Mars. At its summit is a complex caldera about 80 km across, consisting of several nested craters formed when the top of the mountain collapsed into empty magma chambers after giant eruptions.