Mauna Kea Summit
Mauna Kea is so far above sea level you have to stop at a halfway point for three hours to help you acclimate to the elevation. If you don't acclimate for long enough, (three hours being a safe amount of time) the effects of the thin air will get to you and you'll have to quickly come back down. They heavily stress the need for four wheel drive to get to the top but that's because four wheel drive is more gentle on the brakes heading back down. One could easily make it up to the summit in a car, it just wouldn't be safe or recommended. The way down is long and steep and can be double tricky to navigate if you're oxygen deprived. The conditions at the summit of Mauna Kea are so harsh because while Mauna Kea isn't the highest mountain in the world, it is the tallest. Measured from peak to base it's approximately 32,696 feet. If you consider it's base at the Hawaiian Trough but some people measure it from the root of the mountain (deep underground) and suggest it's actual height is 56,447 feet. If you are pregnant, in poor health, or under the age of 16 you should not go past the Visitor Information Station. The station is also where you should spend a few hours acclimating. Altitude sickness is very likely, driving back down the mountain will cure this. You will feel weary, but if it gets too intense come back down.