Olympus Mons.
What is the biggest mountain in the world? Most would say Mount Everest. This answer is correct, but only from a certain point of view. According to the ranking of the highest peaks of the Solar System, the Earth's peak occupies the 11th place, and it is not a Mount Everest.
The highest peak of our Earth belongs to Mauna Kea which is volcano located in the Hawaiian archipelago, on the island of Hawai'i. The summit of the Mauna Kea volcano rises 4205 m above sea level, but at the same time 10 203 m from the bottom of the ocean.
The title of the highest planetary peak in the Solar System belongs to the volcano, lying on the western hemisphere of the Mars - Olympus Mons.
In the nineteenth century, when observations of the Martian mountains were made, this volcano was initially baptized the name Nix Olimpica, which means "olimp snows". The Mariner 9 satelite arrived in orbit around Mars in 1971. Large sandstorms did not allow any structures to be observed on the surface of the planet. With the improvement of the weather and reduction of the storms level, we could see the pictures of the structures that were the largest on the planet, among others, a huge volcano, which name in 1972 was changed to Olimpus Mons meaning Olimp Mountain.
Olympus Mons is a shield volcano located on the volcanic Tharsis plateau. It was created as a result of prolonged and slow lava flow, which over the years created a mild volcanic profile of 5 ° inclination angle. The last recorded eruption of this volcano is estimated between 200 and 100 million years ago.
The volcano is asymmetrical, which means that its crater is not in the middle of the structure, but it is 85 km long, 60 km wide, and is deep about 3 km. The base of the volcano is surrounded by circular depressions about 2 km deep. Interestingly, the volcano embankment is so heavy that it makes the structure dent in the planet's crust.
The size of this object is caused by the long-term lava flow constantly increasing its proportion. The height of the volcano is determined on the basis of the reference point from the equator due to the lack of water level as in the case of Earth. According to this dependence, its height is set at about above 21 km.
Its surface is so large that standing on its top, we would not realize that we are on a huge mountain because its slopes extend beyond the visible horizon.
The only object higher than Olympus Mons is not on the planet, but on a Vesta planedoid located in the asteroid belt. Vesta has an elevation reaching 23 km in height, and its origin is caused by the impact of another object to Vesta, which resulted in a change in the shape of the planetoid structure.
References:
[1]http://www.planetary.brown.edu/pdfs/4617.pdf
[2] http://www.naukatolubie.pl/czerwony-wulkan/
[3] https://www.lpi.usra.edu/meetings/lpsc2011/pdf/2202.pdf