Olympus Mons the height of Mauna Kea as measured from its base on the ocean floor). The total elevation change from the plains of Amazonis Planitia, over to the northwest, to the summit approaches . The summit of the mountain has six nested calderas (collapsed craters) forming an irregular depression × across and up to deep. The volcano's outer edge consists of an escarpment, or cliff, up to tall (although obscured by lava flows in places), a feature unique among the shield volcanoes of Mars. Olympus Mons covers an area of about , which is approximately the size of Italy, and it
Mons Massicus Mons Massicus Mons Massicus, a mountain ridge of ancient Italy, in the territory of the Aurunci, and on the border of Campania and Latium adjectum attributed by most authors to the latter. It projects south-west from the volcanic system of Rocca Monfina (see Suessa Aurunca) as far as the sea, and separates the lower course of the Liris from the plain of Campania. It consists of limestone, with a superstratum of pliocenic and volcanic masses, and was once an island; its highest point is 811 meters (2661 feet) above sea-level. It was very famous for its wine in ancient times.