Olympus Mons, Mars. Artwork of Olympus Mons (darker area, top centre), the largest known volcano in the Solar System. It is found on Mars, the fourth planet from the Sun. Its summit rises 27 kilometers (km) above the surrounding plains (Mount Everest is 8.8 km high), and the base measures 600 km across. Shortly after sunrise, Olympus Mons produces long shadows (bottom centre). To the left of the volcano is a region of ridges and hills known as the Lycus Sulci (rough area, far left). The western margin of Lycus Sulci is next to a smoother, lower elevation known as the Amazonis plains (bottom left).