If you think Mount Everest is something to write home about, take a look at Olympus Mons. Standing at an incredible 27 miles high, this ancient Martian volcano is three times the size of Everest, making it the tallest mountain in our solar system — by a lot.
Olympus Mons is said to have reached such staggering heights the same way volcanoes form here on Earth — minus one critical difference. Mars doesn't have plate tectonics. So instead of shifting over time to create a mountain range, Olympus Mons probably sat over a volcano-forming "hot spot" for a really long time.