IF YOU’RE LOOKING FOR A LEG-BUSTING, AIR-SUCKING SLOG (AND SOME GORGEOUS VIEWS), THIS LIST IS FOR YOU.
Distance: 27.5 miles
Vertical gain: ~6,500 feet
Located on one of Colorado’s famous “fourteeners” (mountains that kiss the sky above 14,000 feet of thin air), the Mount Evans Scenic Byway is the highest paved road in North America. The distance plus that rarified air ranks it among the toughest to tackle.

Distance: 28.5 miles
Vertical gain: ~6,200 feet
Thousands of cyclists make the pilgrimage up this mighty ascent, which is a favorite among pro training camps, each year. The average grade is just 4.1 percent, but it’s steepest near the top as you reach the summit. The scenery, which includes thousands of iconic saguaro cacti and spectacular rock formations, is second to none.

Distance: 12.7 miles
Vertical gain: ~5,200 feet
This remote climb has the reputation as being the most difficult in the state of California. Situated in one of the deepest valleys in the US and surrounded by 14,000-foot snow-capped peaks, it’s also one of the most magnificent climbs in the world.

Distance: 7.9 miles
Vertical gain: ~3,500 feet
This towering gem in the Adirondacks is as long and hard as Alpe d’Huez, and when you crack the lush and fragrant heavily forested sections, equally scenic.
Distance: 24.1 miles
Vertical gain: ~5,100 feet
At nearly 6,700 feet, Mount Mitchell is the highest peak east of the Mississippi River. The summit sits at the dead end of Mount Mitchell State Park road, the highest legal paved road in the eastern United States. It’s the leg-breaking highlight in the annual 102.7-mile Assault on Mt. Mitchell event.
Distance: 7.6 miles
Vertical gain: ~4,700
Among the most difficult hill climbs in the US, if not the world, Mount Washington has an average grade of 12 percent with extended stretches of 18 percent. The last 50 yards snake up 22 percent en route to the welcome center at the summit, where high winds are common.
Distance: 43 miles
Vertical gain: ~13,800 feet
This mammoth volcanic monster is renowned as the hardest climb on the planet. As if the sheer elevation wasn’t hard enough, the surface turns to powdery volcanic rock about five miles from the top, making that final stretch extremely slow going. One trip to the top equals nearly four Alpes d’Huez.
Distance: 7.8 miles
Vertical gain: ~4,300 feet
This high mountain pass in the Italian Alps is one of the legendary climbs in the Giro d’Italia. Originally created for farmers, it is very narrow and includes punishing 18 percent grades.
Distance: 13.4 miles
Vertical: ~5,000 feet
This brutal climb is one of the Tour de France’s most iconic landmarks and has been featured in numerous pro races. Reaching the summit is made especially challenging by the sheer exposure at the top, where riders have zero protection from frequent strong winds and the beating sun.
Distance: 9 miles
Vertical gain: ~5,600 feet
This Balkan brute averages nearly 12 percent and ramps up to 20 percent as you work you way up to its sharp granite pinnacle more than 8,000 feet in the air.
Distance: 15.1 miles
Vertical gain: ~5,900 feet
This hulking ascent has made many appearances in the Giro d’Italia and punishes riders with a whopping 48 hairpin bends. The last three miles are at a lung-busting altitude, making it all the more challenging to reach the summit that sits above 9,000 feet.
Distance: 10.7 miles
Vertical gain: ~4,500 feet
This storied Giro d’Italia climb is one of the highest paved roads in the Alps. It is not only relentlessly steep, averaging nearly 8 percent and seldom dipping below 7 percent, but also is often freezing cold (and snowing) when racers tackle its slopes in May.
Distance: 51.6 miles
Vertical gain: ~10,500 feet
Colombia is known for its climbers, which comes as no surprise when you consider the terrain features endless ascents like Alto de Letras, which cracks the clouds at more than 12,000 feet elevation and is considered one of the longest climbs in the world.
Distance: 7.8 miles
Vertical gain: ~4,100
With an average gradient of just over 10 percent and a maximum pitch of nearly 24 percent, the Alto de l’Angliru is a contender to be the toughest climb in Spain. It’s made a few appearances in Vuelta a Espana and is so brutal (particularly to descend) British pro rider David Millar reportedly tore off his race number at the summit in 2002 to protest its inclusion in the race.
Distance: 21.9 miles
Vertical gain: ~6,300 feet
Pro Tour riders have tackled this Alpine climb myriad times over the years. This one starts with a 10 percent kick and averages 5.5 percent, saving the toughest stretches for the ones approaching the summit.
Distance: 12.9 miles
Vertical gain: ~4,800 feet
This climb, which is inarguably one of the toughest climbs in Southern California, is one of the most feared in the Tour of California. One rider after another comes undone as the road ramps up to 10 to 14 percent for extended stretches en route to the ultimate summit at Mount Baldy Ski Area.
Distance: 36 miles
Vertical gain: ~10,000 feet
Part of the annual “Cycle to the Sun” ride, this volcanic mountain climb that starts from Maui’s North shore Pa’ia is considered one of the longest, most challenging in the world. Though the average gradient isn’t too tough at 5 percent, it’s very long. And the hardest part is the last kick to the summit, when fatigue has set in and you have the least amount of oxygen.
Distance: 11.7 miles
Vertical gain: ~4,600 feet
This Pyrenees beast made its first Tour de France appearance in 1910 and is now among the most visited climbs in the history of the Tour. The pass is the highest road in the Central Pyrenees.
Distance: 13.5 miles
Vertical gain: ~5,500 feet
Soaring more than 10,700 feet into the sky, Alto de la Linea is situated in the central range of the Andes mountains and is regarded as a relentless challenge by Colombian cyclists, as this towering mountain gets harder the higher you go.
Distance: 1.4 miles
Vertical gain: 980 feet
This historic British brute proves you don’t have to be long to be a bear for bike riders. The first two switchbacks greet you with 25 percent grades, which is just a warm up for the next set, which hit and exceed an astonishing 30 percent pitch.
Distance: 8.5 miles
Vertical gain: ~3,500 feet
The Tour de France’s most iconic climb, Alpe d’Huez forces riders to tackle 21 leg-breaking switchbacks in order to reach its Alpine summit. It’s a bucket list climb for hardcore cycling fans.
Distance: 6 miles
Vertical gain: ~3,200 feet
It’s not very long, but it’s terribly steep, with an average incline of 10 percent, a max of 17 percent, and 3 miles that average over 13 percent. Some have called its finishing stretch the hardest in the country outside of Mount Washington.
Distance: 41 miles
Vertical gain: ~11,350 feet
Soaring out of the Venezuelan Andes, Pico el Aguila has an average grade of 5.2 percent and hits a maximum of 13 percent as you pedal through the thin air to the summit that sits above 13,000 feet.
Distance: 65 miles
Vertical gain: ~10,700 feet
This East Asian behemoth travels from the city of Hualien to the summit of Wuling Mountain and is home to the Taiwan KOM Challenge, what is considered by many to be one of the hardest climbing races on the planet.
Distance: 62 miles
Vertical gain: ~11,800 feet
This huge Himalayan ascent is not very steep at just 3.6 percent average gradient, but it goes on forever as you pedal from Nepal into Tibet for a metric century. It is one of the longest uphill cycling routes on Earth.
[Gravel Sportives Are Here, and They Might Be the Best Kind of Cycling Event]
Distance: 16.1 miles
Vertical gain: ~5,050 feet
Situated in Bern, this Alpine pass winds through Swiss mountains and frequently receives heavy snowfall, so is usually closed during winter months. It is a favorite in the Tour de Suisse, and is the only direct road across the Bernese Alps between Bern and Valais.
Distance: 28 miles
Vertical gain: ~7,700 feet
The highest peak in Spain is found towering 12,200 feet above Tenerife in the Canary Islands. This volcano is currently the preferred training ground of elite pro cyclists and teams, including the ever-dominant Team Sky.
Distance: 6.5 miles
Vertical gain: ~4,000 feet
Regarded as one of the most difficult climbs in Europe, the Zoncolan has featured in both the Giro d’Italia and the Giro Rosa. The average grade is 11.5 percent and it sits stubbornly at nearly 20 percent for more than a half a mile, with the upper stretches exposed to the elements.
Distance: 13.3 miles
Vertical gain: ~5,800 feet
This Alpine climb is one of the most arduous around, as it not only has an average grade of more than 8 percent, but also challenges those who want to conquer its slopes with harsh weather, hairpin turns, and cobbles.
Distance: 1.2 miles
Vertical gain: ~1,000 feet
This sucker is a wall. It boasts an average gradient of more than 15 percent and hits you with a peak pitch of 25 percent. It’s featured in Giro di Lombardia in 1960, and was removed three years later as bicycle gearing of the time forced many cyclists to walk it. It has since returned, but remains a fearsome climb even for the pros.
