Olympus Mons was the highest volcano on Mars and the largest known volcano in the solar system.
It was 21,171 meters above the Martian datum plane and over 10,000 meters higher than Mount Everest, the highest mountain on Earth.
It was a veritable behemoth. Even if you stood on Earth and observed the planet with a telescope, you can still see Olympus Mons.
However, unlike Mount Everest, which was steep and difficult to climb, Olympus Mons had a gentle slope, so it was very easy to climb.
Its biggest feature was just being too high and too big. Climbing Olympus Mons was exhausting and time-consuming. But this was not a big problem for Ling Jiu and Niu Ben, as both could fly.
The two climbed to the crater, and a dark sinkhole appeared at the bottom of the crater. It was a passage leading to the inside of Olympus Mons.
