Hello ! More than a month ago I cycled the World's hardest climb. I've written a description about it and embed my trailer video in the middle of the description Have pleasure it and thanks for watching ! Mauna Kea (4205 m) is situated just at the opposite side of the Earth considering from Europe, but I think the Hilo – Mauna Kea ascent can be found on several cycloclimbers’ bucketlist, because based on the climbs’ collections and databases of salite.ch and climbbybike.com this is the hardest / toughest ascent of the world for a road bike (?) or touring bike. Its difficulty score is 1,5 times higher than the Alps’ hardest paved climb (Grosser Oscheniksee) and 2 times higher than the Ovaro climb of Monte Zoncolan or the climb of Angliru ! During the 69 km long ascent You have to climb 4193 m heightdifference and in the last few kms the less oxygen makes is harder (those who attempt this ascent they need acclimatisation!). In the last 20 kms the cyclist has to climb 2000 m heightdifference, 7 kms of it has no pavement, but that is dirt road with sand where the tires sink several times. Because of the dirt road section many cyclists suggest to use min 32 mm wide tires if You don’t plan to change the bike by the start of the dirt road, at the Visitor Center. I used 32 mm wide Schwalbe Marathon tires. There is another thing that makes the climb hard: after leaving the beach of Hilo, the next place to get water, buy snack, etc. is situated 55 kms farther at the height of 2800 m. That’s the reason that several cyclists that cycled up to the summit suggest those wh would like to cycle up to have support car that carries the food, water, drink and clothes for the descent (if descending would start in the evening). Those who would like to cycle up without support need to carry min. 4-5 liters of water / drink by the start. (I did it this way.) Mauna Kea is considered the tallest mountain of the Earth, because if we measure it from its bottom (can be found under the ocean), it’s heightdifference is more than Mount Everest’s or any other high mountains’ heightdifference. The volcano is situated in the Big island of the Hawaii islands next to the other high volcano, Mauna Loa that is one of the active volcanoes of the World and produces lava-flow every day. The start of the ascent can be found by the beach of Hilo which is considered one of the most rainiest places of the Earth. There are several observatories at the summit; it is said the summit offers one of the most clear, best opportunities for star-watching or stargazing. By sunset several cars drive up for enjoy the perfect sunset. Only one ascent goes up to the top, but there are two places to start: the longer begins at the sunnier, hotter Kona side and the other (69 km long) starts at the rainier, Hilo side. During the several hour / one day long ascent the weather and the plants change several times: by the Hilo side it starts along with wonderful flowers and huge trees and than it changes for a cloudy, humid section. The eastern climb, starting at the Kona side begins along hot lava fields. The middle section can be sunny and cloudy too ( I have both) and the summit is usually clear, sunny, but as the Sun goes down it could be cold (only few degrees celsius above zero). At last a subjective opinion: why this climb is considered to be the hardest climb of the World ? Reaching the Visitor Center (2800 m) the cyclist feels / shoudl feel only a little bit tired, but after starting the dirt road section the lack of oxygen, the fact that the tires several times sink in the sand and the dirt road is sometimes 13-15% (once 20%) steep increase tiredness. Reaching the paved road again (at 3554 m) the cyclist has to climb more than 650 m heightdifference on sometimes 12-14% steep road which feels as it would be ca. 18% steep because of the less oxygen and if the cyclist gets headwind (I got) than it could be is very-very hard! (Monte Zoncolan „offers” 1055 m heightdifference for the last ca. 8 kms (avg. 13,1%), here You can feel ca. similar difficulty in the last 8-10 kms, but when You reach that last section You already had 3100-3200 m heightdifference in your legs. Big island offers another long and high finishing ascent: that goes up on the mountain of Mauna Loa, but on that road You can’t cycle up to the summit; the road ends under 3400 m and the view is much more less spectacular than at the summit of Mauna Kea and the ascent is not so hard than the other. I hope You enjoy the video and find the description useful.