Gunma’s mountains cover the greater part of the prefecture, rising from the flat Kanto plain in the south to volcanic ridges and alpine wetlands along the northern border with Niigata and Fukushima. The variety of terrain is wide — ancient shield volcanoes with caldera lakes, narrow river gorges cut by glacial meltwater, and elevated marshes that exist only because the altitude keeps them frozen for half the year. For outdoor travelers, Gunma is one of the most rewarding prefectures within two hours of Tokyo.
Oze National Park
Oze is Japan’s most famous alpine wetland, a high plateau stretching across the borders of Gunma, Fukushima, and Niigata prefectures at elevations between 1,400 and 1,900 meters. The landscape is defined by wide, flat marshes intersected by wooden boardwalks, surrounded by low mountains that are never quite far enough away to feel distant.
Seasons and Highlights
The park is only accessible from roughly early June through late October, when the access roads and trails are clear of snow. Within that window, two periods draw the largest numbers of visitors.
Early June brings the bloom of mizubasho (Asian skunk cabbage), a plant that produces large white spathes — more leaf than flower — across the wetland floor. The bloom lasts two to three weeks and transforms the marsh into something resembling an impressionist painting: white and green on brown water, with mist sitting low over the surface in early morning. The plant also has a pungent, sharp smell that carries across the trail.
October brings the autumn color season, when the wetland’s surrounding forests and low hills shift through gold, orange, and red. The kochia bushes on the marsh fringes turn crimson, and the whole plateau takes on a warm, end-of-season atmosphere. This is the most photographed season in Oze and also the most crowded.
The Boardwalk Trail
The standard circuit trail covers approximately 8 kilometers and takes three to four hours at a comfortable pace. The route is almost entirely on elevated wooden boardwalks that protect the fragile wetland soil from foot traffic. The terrain is flat and the walking is easy; there are no significant elevation changes on the main marsh circuit.
Several huts and rest points along the route sell simple food — onigiri rice balls, instant noodles, canned drinks — which matters because the trailheads can be several hours from any town. Carry water and snacks regardless.
Access and Practical Information
No private cars are permitted beyond designated parking areas, which are themselves some distance from the trailheads. The standard approach is by bus from Numata Station on the JR Joetsu Line. The journey takes approximately 90 minutes and costs ¥1,700. Buses run from late May through October on a timetable that changes by season; check the current schedule before traveling.
Entry to the park is free. The main trailheads are at Hatomachi-toge (Gunma side) and Oze-guchi. Accommodation inside the park at mountain huts is available for walkers who want to stay overnight and experience the wetland at dawn.
Footwear should be trail shoes or light hiking boots. The boardwalks can be slippery when wet. There are no facilities for shoe rental or significant equipment purchase near the trailheads, so come prepared.
Mt. Akagi
Akagi is one of the most geologically interesting mountains in the Kanto region. It is a broad shield volcano rather than the classic conical form, and its summit plateau holds a caldera with two distinct lakes — Onuma, the larger, and Kanna, the smaller — surrounded by forests that have been designated a quasi-national park.
Akagi Shrine
The lakeside shrine at Onuma is one of Gunma’s most visited, particularly during autumn when the approach road lines up with the foliage canopy in a way that makes for dramatic photography. The shrine has a long history and sits in a grove of old cedar and fir trees beside the water, its wooden gate reflected in the lake surface on still mornings. It is accessible year-round and adds a cultural dimension to what would otherwise be a purely natural destination.
Autumn Foliage
The peak color period on Mt. Akagi runs from mid-October through early November, approximately two weeks before the foliage peaks in lower-elevation areas. The caldera basin concentrates the color — the surrounding rim reflects in both lakes, and the walking paths through the forest at this time are exceptional. This is one of the best foliage spots in Gunma precisely because the color is dense and the water reflections amplify it.
Winter Ice Fishing
From January through February, Lake Onuma freezes to sufficient depth for ice fishing. The local fish of choice is wakasagi (a smelt-like freshwater fish), which is caught through small holes drilled in the ice and is eaten tempura-fried, either at lakeside facilities or taken home. Ice fishing sets and instruction are available for rent from operators at the lake. This is a popular winter activity for Japanese families and offers visitors a genuine seasonal experience rather than a staged one.
Access
Mt. Akagi is most easily reached by car from Maebashi (approximately 40 minutes), which is on the JR Ryomo Line from Takasaki. Bus services to the summit area are limited and infrequent; a rental car from Maebashi or Takasaki is the practical option. Roads are well-maintained and signposted.
Lake Haruna
Lake Haruna occupies a volcanic crater in central Gunma, sitting at 1,084 meters elevation above the Ikaho Onsen area. The crater rim creates a near-perfect circle of forested hillside around the lake, giving it an enclosed, private atmosphere even in summer.
Boat Rental and Lake Activities
Rowboats and pedal boats are available for rental at the lakeside at ¥1,000 for 30 minutes. On calm days the reflections of the surrounding forest in the water are extraordinary, and spending an hour on the water is one of the more peaceful ways to pass time in Gunma. Swan-shaped pedal boats are common at Japanese recreational lakes and Haruna is no exception; they are cheerful and surprisingly easy to navigate.
The lakeside also has a small amusement area with food stalls, a rope-way to a viewpoint above the rim, and simple accommodation options. It is a mild, family-friendly destination that does not require significant hiking preparation.
Haruna Shrine
A short drive from the lake, Haruna Shrine sits deep in a narrow rocky gorge where the landscape changes dramatically. The approach path winds between enormous moss-covered boulders, passing stone lanterns that have been there long enough to sink and tilt at angles. The shrine buildings themselves are pressed against the cliff face at the gorge’s end, with a waterfall visible above them in wet weather.
The combination of geological drama and aged religious architecture makes this one of the most atmospheric shrine visits in Gunma. The gorge also stays noticeably cooler than the surrounding area in summer, which is relevant in July and August.
Autumn and Winter
Lake Haruna’s surrounding forest reaches peak foliage in late October. When the crater rim is fully colored, the reflections in the lake create a symmetrical display that draws significant numbers of photographers. In winter, the lake freezes reliably and hosts both ice skating and ice fishing, similar to Akagi’s Onuma. Rental ice fishing equipment is available, and the activity runs from late December through mid-February in most years.
Minakami River and Gorges
The Tone River originates in the mountains of northern Gunma and flows south through a series of progressively wider valleys before reaching the Kanto plain. The upper section, near Minakami, passes through steep-sided gorges of considerable beauty and provides some of the best whitewater for outdoor sports in the Tokyo metropolitan area.
Rafting on the Tone River
Commercial rafting on the upper Tone River runs from late April through October. The river offers Class III and IV rapids depending on the section and water levels, with the spring snowmelt in April and May creating the most powerful flows. Several outfitters in Minakami town offer half-day and full-day rafting trips, typically priced between ¥6,000 and ¥10,000 per person including equipment and guide. No prior experience is required for most half-day trips.
Canyoning
Canyoning — descending river gorges by a combination of swimming, sliding, jumping, and rappelling — is available in the side gorges off the main Tone valley. The Dorokawa and Nanamagari gorges are popular canyoning routes that include natural rock slides and short plunge pools. Sessions run about three hours and require no special skill, though a reasonable level of physical fitness is helpful. The season runs from June through September.
Canyon Walking
For those who prefer to stay dry, several gorge routes in the Minakami area are accessible as walking paths. The Tanigawadake mountain area, accessible by ropeway from Doai Station on the Joetsu Shinkansen, offers gorge-edge walking with views down into the river valleys. This is one of the few areas in Gunma’s mountains accessible without a car from the shinkansen line.
Seasonal Highlights
| Season | Best Spot | What to See |
|---|---|---|
| Early June | Oze National Park | Mizubasho (skunk cabbage) bloom |
| Late July–August | Lake Haruna / Minakami | Hiking, water activities, cool air |
| Mid-October | Mt. Akagi, Lake Haruna | Autumn foliage and lake reflections |
| Late October | Oze National Park | Autumn color on the wetland plateau |
| January–February | Lake Onuma (Akagi), Lake Haruna | Ice fishing, ice skating |
Practical Tips
Car is essential for most natural sites. Oze National Park is accessible by public bus from Numata Station, but Mt. Akagi and Lake Haruna have very limited public transport. A rental car from Takasaki or Maebashi dramatically expands what is achievable in a single day.
Start early at Oze. The park trailheads fill quickly during peak season. Arriving at the first bus departure of the morning, typically around 06:30–07:00, means less crowding on the boardwalks and better light for photography.
Clothing layers. The elevation of Oze (around 1,400 m) and the Akagi caldera means temperatures can be 5–10°C lower than in Takasaki even in summer. Carry a light windproof layer. In October, bring warm clothing.
Road conditions. Mountain roads to Lake Haruna and Mt. Akagi can be icy in autumn and are sometimes closed in heavy snowfall. Check road condition reports before driving between November and April.
Combining with onsen. Gunma’s nature sites and onsen resorts complement each other well. A morning hike at Mt. Akagi or Lake Haruna pairs naturally with an afternoon soak at Ikaho Onsen, which is in the same part of the prefecture. Oze visitors can return through Minakami and stop at one of the valley’s eighteen onsen sources for a recovery bath.