Here's something I just stumbled upon a few minutes ago. Its Olympus Mons, Mars' largest mountain. Olympus Mons is also the largest volcano in the solar system and the 2nd tallest mountain in the solar system (behind the Rheasilvia peak on the asteroid 4 Vesta). Olympus Mons is a shield volcano and was formed the same way that the Hawaiian islands were, by lava flows hardening and building up over hundreds of millions of years. The difference is that while the Hawaiian chain was formed by Earths crust moving over a hot spot in the mantle, Mars does not have mobile tectonic plates so the hotspot that releases lava is always in the center of the mountain. Olympus Mons is located near the martian equator and is 370 miles wide and 13 miles tall, with cliffs up to 5 miles tall. The base covers an area roughly the size of the state of Arizona and is 2.5 times taller than mount Everest. The atmospheric pressure at the highest point is estimated to be 0.03kPa, which is 12% of the average martian atmospheric pressure of .6kPa. What's interesting about this is that the air pressure at the summit of Olympus Mons is a much higher percentage of the surface pressure than it would be on Earth. The atmospheric pressure on Earth at an altitude of 13 miles is approximately 4.5kPa, just 4.43% of the average sea level pressure of 101.33kPa. This happens because the acceleration due to gravity on mars in 3.7m/s2, less than half of that on Earth, which increases the scale height of Mars' atmosphere, so there is relatively higher atmospheric pressure at higher altitudes.
It's amazing to think that there are mountains out there on other planets that dwarf anything we have on Earth. I've always been interested in space but my interest just peaked (pun intended) as I look out at the night sky and wonder what else is out there.