Mons Huygens Moon further north, which was visited by Apollo 15. The tallest mountain known in the Solar System is in Rheasilvia crater on the asteroid Vesta, which contains a central mound that rises high; Olympus Mons on Mars is nearly the same height, at high. In comparison, Mount Everest rises to altitude above sea level (asl), but is only (base-to-peak) (btp). Africa's Mount Kilimanjaro is about altitude above sea level to the Uhuru peak; also 4.6 km base-to-peak. America's Denali, also known as "Mount McKinley", has a base-to-peak of . The Franco-Italian "Mont Blanc/Monte Bianco" is in altitude above sea level,
Tharsis Montes is about across and stands above the ocean floor. The Tharsis Montes volcanoes lie near the equator, along the crest of a vast volcanic plateau called the Tharsis region or Tharsis bulge. The Tharsis region is thousands of kilometers across and averages nearly above the mean elevation of the planet. Olympus Mons, the tallest known mountain in the Solar System, is located about northwest of the Tharsis Montes, at the edge of the Tharsis region. The Tharsis Montes were discovered by the Mariner 9 spacecraft in 1971. They were among the few surface features visible as the spacecraft entered orbit