Tharsis volcanoes, Mars. Artwork of the Tharsis Montes region on Mars, an enormous volcanic upland. It contains the Tharsis Bulge, on which some of the Solar System's largest volcanoes are located; Olympus Mons (not shown), Arsia Mons (top right), Pavonis Mons (middle) and Ascraeus Mons (bottom). These three volcanoes range in size from 350 to 450 kilometres (km) across and they each have a height of approximately 15 km. The fractures lower right of Pavonis Mons are Noctis Labyrinthus; this region merges with the enormous Valles Marineris canyon system to the east.