What Is Onioshidashi Volcanic Park (Onioshidashi-en)?
Onioshidashi Volcanic Park (Onioshidashi-en) is a lava field formed by an eruption of Mount Asama, located in Tsumagoi Village, Agatsuma District, Gunma Prefecture.
A massive flow of lava from the 1783 eruption of Mount Asama (Tenmei 3) created this unique landscape.
The name is said to come from a legend describing the scenery as looking like “a demon pushed out the rocks.”
Located within Jōshin'etsu-kōgen National Park, it is a popular sightseeing spot where visitors can feel the power of volcanic activity.
At an elevation of about 1,300 m, it is also one of the attractions that makes the area cool and comfortable even in summer.
Top Things to See and Highlights at Onioshidashi Volcanic Park
1. A Vast Lava Field on an Epic Scale! Experience the Power of a Volcano
One of the biggest highlights of Onioshidashi Volcanic Park is the lava field stretching about 5.5 km north of Mount Asama’s summit and covering about 6.8 square km.
Seeing alpine plants growing between the rocks lets you feel the resilience of nature.
① Like Another World! Dynamic Volcanic Scenery
The landscape of rugged volcanic rocks spreading out before you feels truly extraordinary and otherworldly.
On clear days, you can see Mount Asama in the distance.
When conditions are good, you may also get wide views of the surrounding mountain ranges.
② Walking Trails You Can Explore in About 30 to 60 Minutes
Inside Onioshidashi Volcanic Park, there are walking courses you can choose based on how much time you have.
You can enjoy routes that take around 30 minutes, or extend your walk to the Okunoin approach (Honō Kannon) on a course of about 60 minutes.
The park features well-maintained walking paths, making it easy to explore even with family.
2. Must-See Spots at Onioshidashi Volcanic Park
① Asama-yama Kannon Hall (Asama-yama Kannon-dō)
On an elevated area inside the park, you will find the Asama-yama Kannon Hall.
- It is loved as a place where visitors can quietly offer prayers while reflecting on the history of eruptions
- You can spend a peaceful moment together with the lava scenery
② Lava Tunnel and Unusual Rock Formations
You can walk among strangely shaped rocks and gaps in the lava created by volcanic activity.
- Passing through areas where rocks taller than a person are piled up feels a bit like cave exploration
③ Scenic Viewpoints with Great Mountain Views
From lookout spots further along the walking trail, you can enjoy:
- Views of Mount Asama
- Surrounding mountain ranges and highland scenery
You can enjoy these views.
These spots are also popular for photos, with a striking contrast between lava rocks and mountains.
3. Seasonal Scenery at Onioshidashi Volcanic Park
① Spring (Snowmelt to Early Summer)
Fresh greenery is beautiful, making this a great season for walking.
Alpine plants begin to bloom between the volcanic rocks.
② Summer (Summer Season)
The cool highland breeze feels pleasant, and the area is also recommended as a summer escape from the heat.
The contrast between the blue sky and black lava is impressive, and you can enjoy a comfortable walk.
③ Autumn (Fall Foliage Season)
The yellow leaves of larch trees and others are beautiful, and the contrast between yellow-colored trees and black lava stands out.
Depending on the weather and timing, it may overlap with the first snowfall on Mount Asama.
④ Winter (Snow Season)
Onioshidashi Volcanic Park covered in snow has a beauty that feels like another world.
Snow covers the lava, making the black-and-white contrast even more striking.
It is open year-round, so you can visit in winter as well.
4. Nearby Attractions Around Onioshidashi Volcanic Park
There are many attractive sightseeing spots scattered around Onioshidashi Volcanic Park.
✅ Karuizawa (Nagano Prefecture): Popular as a resort area
✅ Kusatsu Onsen (Gunma Prefecture): Fun to stroll around the hot spring town
✅ Tsumagoi Village Cabbage Fields: Expansive countryside scenery
5. Tips to Avoid Crowds
Weekends during Golden Week and the autumn foliage season can be busy with many visitors.
If you visit on a weekday morning, you can usually enjoy a more relaxed walk.
Even in busy seasons, the park’s grounds are large, so crowding on the walking paths tends to be less intense.
Useful Information for Travelers
Access (How to Get to Onioshidashi Volcanic Park from Tokyo)
By Train + Bus
- Tokyo Station → Karuizawa Station (Hokuriku Shinkansen: travel time varies by service)
- Karuizawa Station → Onioshidashi Volcanic Park (local bus: travel time varies by service)
If using the JR Agatsuma Line, you can also access the park by bus from Manza-Kazawaguchi Station.
By Car
- You can access the park via the Oni-Oshi Highway from the Jōshin-etsu Expressway “Usui Karuizawa IC”
- Parking available (about 750 spaces, free)
The Oni-Oshi Highway is a toll road (standard cars: about 280 to 370 yen depending on the section).
Opening Hours and Admission Fee
- Opening hours: 8:00–17:00 (last admission 16:30)
- Admission fee: Adults (junior high school students and older) 700 yen / Children (elementary school students) 500 yen / Preschool children free
You may be able to receive a discount by presenting a coupon or other discount ticket.
Manners and Tips for Visiting
- Please avoid walking on the lava outside the designated paths, as it is dangerous
- Because of the high elevation, it is a good idea to bring one extra layer even in summer
- Pets (dogs) are allowed to enter the park (leash required)
Wi-Fi and Facilities
- There are restaurants, rest areas, and souvenir shops inside the park
- Free wheelchair and stroller rentals available
- Because this is a mountain area, mobile reception may be weak in some spots, so downloading a map in advance is recommended
Multilingual Support
- Multilingual guidance may be available
Summary
Onioshidashi Volcanic Park is a spot where you can experience up close the vast lava field created by the eruption of Mount Asama.
You can enjoy walking trails, the Asama-yama Kannon Hall, and beautiful scenery in every season.
It is also recommended to visit together with nearby destinations such as Karuizawa and Kusatsu Onsen.
