Mount Akagi 赤城山 – Cycling The Red Fortress Mountain

Mount Akagi 赤城山 – Cycling The Red Fortress Mountain

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Mount Akagi is the centerpiece of the skyline in the Kita Kanto Region. One of the three Sanmeizan 三名山 or three famous mountains of Gunma, Akagi’s battleship like flattened ridge line defines much of the skyline from any viewpoint in northern Kanto.

With the base of the mountain starting at the Tone and Watarase Rivers around 100 meters above sea level Akagi’s gentle lower slopes give way to a jagged ring of peaks summiting at 1,824m above sea. Within the rugged caldera rests a high alpine lake, Onuma 大沼 at over 1,300m above sea.





Zen Factor

Climb Score Card from our full article on the 14 Best Cycling Climbs in Japan (Hint, Not Mt Fuji!).

Washbasin at the Akagi Onuma Shrine.
Washbasin by the Onuma Lake at the Akagi Shrine.

Mount Akagi Annual Hill Climb Race

Cyclist from around Japan know of Mount Akagi for the Annual Hill Climb Race held each September up the main Route 4 road.

Akagi Hc
Over 1,300m gain in under 21km!

Routes Up, Down, and Around Mt Akagi

While the hill climb race has an amazing opportunity to climb the main Route 4 up Akagi on a closed road around thousands of other cyclists, the rest of the year this is far from the best route up Mt Akagi.

Below are a few suggested routes when it comes to having the best experience climbing or riding around Mt Akagi.

Mt Akagi from the top of Mt Kanayama in Ota
Mt Akagi from the top of Mt Kanayama in Ota.

Routes on Mt Akagi

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An overview of the many routes on and around Mt Akagi.
  1. Mount Akagi Main Road | Route 4
  2. Mount Akagi Old Road | Route 16
  3. Mount Akagi North Road | Route 251
  4. Mount Akagi Panoramic Road and Backside Road |Route 62
  5. Mount Akagi Dirt Road Numao River Rindo| 沼尾川林道
Mount Akagi to the right from above the Tone River.
Mount Akagi to the right from above the Tone River.

Mount Akagi Main Road | Route 4

This is the main route and thus the one 90% of all cars will take. This route is in short nowheres near as nice to ride up as the other routes due to the traffic.

That said, this is hands down the most fun (maybe in all of Japan?) road to descend. With two full lanes and often good gaps in the cars and on weekdays hardly enough cars to see them. What more, the pavement on the lower 2/3rds of this road is pristine and you can absolutely let it rip! Our guests that come on tours where we descend this universally rate it as their favorite descent.

So in short, come down this road and go up another way.

The Akagi Miyozawa Shrine.
The Akagi Miyozawa Shrine.

Mount Akagi Old Road | Route 16

The Route 16 is the old road up Mount Akagi. Home to the Akagi Miyozawa Shrine this is my top recommendation for climbing Mt Akagi by bike.

The road has 100 numbered switchbacks to the top, and you can see a video of me riding this route up in the video below.

This route also takes you over the highest pass on Mt Akagi, the Haccho Pass at over 1,500m above sea. That’s a 1,400m gain if you come from Kiryu City!

Mount Akagi from the top of Mount Chausu in Kiryu City.
Mount Akagi from the top of Mount Chausu in Kiryu City.

Mount Akagi North Road | Route 251

The main route from the north side of Mt Akagi this route is a great option for those looking to drop into Numata or come up from that side. Often quieter than the main Route 4 but busier than the old road Route 16.

Mount Akagi's caldera lake Onuma.
Mount Akagi’s caldera lake Onuma.

Mount Akagi Panoramic Road and Backside Road |Route 62

This is the route I like to call the “Akagi Lap.” At just over 100km and over 2,000m gain it’s a big day with mostly rolling hills and moderate climbs and one big climb up and over the backside road Route 62.

Fair warning that this route passes a lot farms when on the westside of the mountain. Some have epic views, and some smell like farms. But overall the beauty far outweighs the occasional manure smell.

A great stop along the way on this route is the roadside foot bath in tiny onsen town of Nango Onsen on the backside of the loop.

Nango Onsen Foot Bath on Mount Akagi.
Nango Onsen Foot Bath.

Mount Akagi Dirt Road Numao River Rindo| 沼尾川林道

You may only see the three roads we’ve discussed so far on your maps when you look at roads to the top of Mt Akagi, but what if I told you there is a 4th unpaved road to the top?

From the west side of Mt Akagi along Rt 157 群馬県道157 you will pass the Akagi Campgrounds. Continue heading up the road (east) until you come across the sign pictured above and then hop off the pavement for about 10km of unkempt gravely forest road goodness. (Location pin for start of dirt road)

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Signs at the entrance of the Numao Rindo.

This road is/was a full fledged service road for the water company, but seems to have gone the way of forgotten roads in the area so be sure to bring plenty of water and snacks and be ready for some possible hiking in spots!

Akagi Shrine Lantern.
Akagi Shrine Lantern.

Osusume Recommended Course おすすめ〜

From the Akagi Miyozawa Shrine ride up the old Route 16 to the Lake Onuma. From there take route 16 down until the first traffic light. At the light turn left and take the Akagi Panoramic Highway across and back to the Miyozawa Shrine.

Strava Route File:

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45km and 1,400m gain, not too shabby!
View from the old road high above the Tone Valley below.
View from the old road high above the Tone Valley below.

Seasons and road closures on Mount Akagi

Mount Akagi is unique in its altitude and distance from the main ridge of mountains that bisects Japan and forms the Gunma/Niigata/Nagano borders. With this, Akagi has a very unique weather pattern on it, making for sunny dry days most of the spring, fall, and winter in comparison to the nearby mountains in Kanto Area.

In the summertime you can expect the heat in the lower Tone Valley below to reach well into mid 30s to even low 40s. Meanwhile, up at the caldera lakes on Mt Akagi it is consistently 10-15 degrees celsius lower.

I have ridden Akagi in every season and can attest to the fact that you can ride up it any month of the year even the dead of winter! Just keep an eye on the snowfall/ice situation in the months of Dec-Apr.

Best Time To Ride

Spring | Mid April to early June

Fall | Mid September to end of November

Road Closures

Though Mt Akagi’s roads are often clear of snow and ice that is not to say that it will not form if a good snow storm makes it in over the ridges to its west.

In general Routes 16 and 251 will close from early to mid December and reopen around mid March to early April.

Route 4 and Route 62 will remain open all year but that does not mean they are treating the road at all times. Know your limits and use best judgement when riding Dec-Apr.

Score Card Breakdown

Gain – 5/5 | From Kiryu or Maebashi over 1,400m gain to the Haccho Pass 八丁峠
Views – 4/5 | There is an amazing opening around turn 70 on the way up that overlooks the whole Kita Kanto Region below. Once atop, the dive into the caldera reveals the hidden lake and red shrine.
Accessibility – 4/5 | From Kiryu it is a 100km loop with around 2,000m of gain going up Rt 16 and down Rt 4. (1h30 direct express from Asakusa Station to Shin-Kiryu Station)
Pavement – 4/5 on the up route 16, 5/5 on the down main route 4. The closest to flying you can find with over 3km of straight pristine 8-10% downgrade. Hands down THE best descent in Japan.
Zen Factor – 5/5, except holidays 4/5

Check out our full guide on the 14 Best Cycling Climbs in Japan (Hint, Not Mt Fuji!).

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