How can you have a vague interest in the solar system and planets (enough to post a question on Quora about them) and not have heard of Olympus Mons?!
Meet Olympus Mons (Mount Olympus) on Mars, at 22 km high, the largest mountain and volcano in the solar system:
It’s a volcano the size of France:
2 1/2 times as high as Mount Everest:
The Moon also has mountains (these are hills but hey, what a cool photo):
The highest mountains on the Moon are over 10 km high, making them significantly taller than any on Earth (Selenian summit shown in green):
Selenian summit is 10,786 m as measured from the Lunar mean surface (the Moon’s equivalent of sea level based on its average radius of 1,734.4 km). This is higher than Mauna Kea as measured from base to peak (10,210 m), and much higher than Everest (8,848 m), so it’s safe to say the Moon and Mars have bigger mountains than Earth.
Even if they’re formed by impactors and volcanoes, rather than plate tectonics.