Sorry Mount Everest — you’re not the king of the solar system. That honor belongs to Olympus Mons, a massive mountain on our planetary neighbor, Mars. Olympus Mons is a giant mound of red dirt and rock. This volcanic behemoth is 24,000 meters, or 80,000 feet tall, which makes it almost 15 miles high. Everest is a mere dwarf in comparison. This giant Martian volcano is either a mountain climber’s wildest dream, or worst nightmare.