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,
Fictional planets of the Solar System while yet others are purely fictional and were never intended as serious hypotheses about the structure of the Solar System. Vulcan was a hypothetical planet supposed to revolve around the Sun inside the orbit of Mercury, invoked to explain certain irregularities in Mercury's orbit. The planet was proposed as a hypothesis in 1859, and abandoned not later than 1915. The name "Vulcan" has been used for various other fictional planets, in and out of the Solar System, that do not correspond to the hypothetical planet Vulcan. The planet Vulcan in the "Star Trek" franchise, for instance, is specified as orbiting