Olympus Mons on Mars is the highest known mountain on the planets of our solar system. The shield volcano has a height of about 22 kilometers above the average ground level of Mars. It's base diameter is almost 600 kilometers wide. From a geological point of view Olympus Mons is still relatively young, and probably evolved about two million years ago.
More information about the different materials.
Elevation: 21287 m
Prominence: 26000 m
Orometric dominance: 122