Marunuma and Suganuma (Gunma Prefecture) Complete Guide｜Thoroughly Explained: Secret Lakes Boasting Honshu’s Highest Transparency
Deep in Katashina Village, Tone District, Gunma Prefecture, located at altitudes exceeding 1,400-1,700 meters, Marunuma and Suganuma are beautiful lakes included in Nikko National Park. Particularly Suganuma boasts the transparency ranked first in Honshu, and its deep blue waters captivate all who visit. This article provides detailed information including the appeal of these two lakes, practical access information, and recommended surrounding spots, incorporating local knowledge.
What Are Marunuma and Suganuma? Basic Information on Gunma Prefecture’s Spectacular Lakes
Formation and Geographic Characteristics of Marunuma and Suganuma
Marunuma and Suganuma are barrier lakes formed when lava flows of andesite discharged by volcanic activity of Nikko-Shirane Mountain blocked the river. Located about 1km apart along National Route 120, just before the Konsei Pass Tunnel, the upstream side (toward Konsei Pass) is Suganuma, and the downstream side is Marunuma.
Marunuma Basic Data:
- Altitude: Approximately 1,430 meters
- Lake surface area: Approximately 0.25 square kilometers
- Circumference: Approximately 2.5 kilometers
- Maximum depth: Approximately 18 meters
- Location: Higashi Ogawa, Katashina Village, Tone District, Gunma Prefecture
Suganuma Basic Data:
- Altitude: 1,731 meters
- Lake surface area: 0.77 square kilometers (some sources indicate 0.63 km²)
- Circumference: 6.5 kilometers
- Maximum depth: 75 meters
- Transparency: Ranked first in Honshu
- Composition: The three constricted sections of Shimizunuma, Bentennuma, and Kitakinenuma are collectively called Suganuma
Achievement of First Place in the New Japan Tourist Attractions 100 Selection
In 1950, when the New Japan Tourist Attractions 100 Selection was established, Marunuma and Suganuma simultaneously achieved the remarkable feat of winning first place in the lakes section. Furthermore, they have been selected for Japan’s 100 Famous Landscapes and 100 Selections of Japan’s Natural Heritage to Preserve in the 21st Century, earning high evaluation as natural landscapes representative of Gunma Prefecture.
The Charm of Suganuma｜A Mystical Lake with Honshu’s Outstanding Transparency
Mysterious Lake Water with Honshu’s Top Transparency
The greatest charm of Suganuma is undoubtedly its overwhelming transparency. Its location in the innermost reaches of the Kanto region and an environment surrounded by rich forests protect the lake from artificial pollution. Combined with its maximum depth of 75 meters, the lake’s surface exhibits a deep blue color, displaying various expressions depending on weather and time of day.
On clear days, the lake bottom is sometimes visible through the surface, and its beauty is praised as “unthinkable for a Japanese lake.” Particularly during the quiet early morning hours, the lake surface mirrors the surrounding mountains like glass, creating a fantastical landscape.
Enjoying Nature at Suganuma Camp Village
The “Suganuma Camp Village” with well-equipped facilities is located on the shore of Suganuma Lake, allowing visitors to enjoy camping while gazing at the lake with exceptional transparency. With not only tent sites but also bungalows, even beginners can safely experience outdoor activities.
At night, the sky fills with stars, and the Milky Way and shooting stars unseen in urban areas can be observed. Due to the high altitude exceeding 1,700 meters, the air is clear and the environment is ideal for astronomical observation.
SUP, Canoe, and Kayak Experiences
SUP (stand-up paddleboard) activities are popular at Suganuma, taking advantage of its transparent lake surface. Riding an SUP across the lake creates the strange sensation of floating in the air.
Canoe and kayak tours are also offered, allowing visitors to enjoy a sense of unity with nature on a private, quiet lake. The high transparency makes it possible to observe the lake bottom while paddling, an experience unique to Suganuma.
The Charm of Marunuma｜A Nature-Rich Lake Displaying Seasonal Expressions
Rich Ecosystem and Fishing Spot
Marunuma is home to diverse fish species including rainbow trout, carp, char, and sculpin, making it an attractive spot for fishing enthusiasts. Both shore fishing and boat fishing are available, with rainbow trout fishing being particularly popular.
The environment surrounded by rich forests is also a treasure trove of birds and small animals. Many visitors enjoy bird watching and nature observation, with different wildlife encounters possible throughout the seasons.
Boating and Lakeside Walks
Boating is also available at Marunuma. The view of surrounding mountains from a rowboat on the lake is exceptional, and particularly during the autumn foliage season, colorful mountain slopes reflect beautifully in the lake surface, creating breathtaking scenery.
Walking paths have been developed along the lakeside, allowing visitors to enjoy nature leisurely on foot. Rest facilities such as Marunuma Lakeside Pavilion provide places to pause and enjoy the scenery.
Fall Foliage Season Spectacular Views｜The Autumn Charm of Marunuma and Suganuma
Peak Season and Color Change Information
Autumn foliage in the Marunuma-Suganuma area typically peaks from late September through mid-October. Due to the high altitude, foliage begins especially early in Gunma Prefecture, marking the beginning of autumn foliage season in the Kanto region.
Peak foliage period:
- Late September: Color begins
- Early to mid-October: Peak season
- Late October: Leaf fall
Beech, rowan, and maple trees lining the lakeside paint the landscape in reds and yellows, creating stunning contrast with the deep blue lake surface. The reflected autumn foliage on Suganuma’s transparent water in particular displays painting-like beauty, attracting many photography enthusiasts.
Best Photography Spots for Fall Foliage
Suganuma Photography Spots:
- Around Suganuma Camp Site: Panoramic view of autumn foliage and lake from the shoreline
- Observation points along National Route 120: Bird’s-eye view of entire lake from high position
- Near Bentennuma: Unique composition created by the constricted terrain
Marunuma Photography Spots:
- Around Marunuma Lakeside Pavilion: Composition with foliage in foreground and Nikko-Shirane Mountain in background
- Near boat rentals: Ideal for capturing lake surface reflections
- Around Marunuma Dam: Contrast between dam and autumn foliage
Early morning quiet hours are optimal for reflection photography, when wind is calm and the lake surface becomes mirror-like. The diagonal light at dusk on foliage also displays exceptional beauty.
Access Methods｜Detailed Explanation of How to Reach Marunuma and Suganuma
Car Access
Car access is most convenient and provides maximum freedom for surrounding sightseeing.
From the Kanto region:
- From “Numata IC” on the Kan-Etsu Expressway, approximately 60km (approximately 90 minutes)
- Proceed toward Nikko on National Route 120
- Via Katashina Village toward Konsei Pass
- Arrive at Marunuma, then Suganuma in order
From the Nikko region:
- Follow National Route 120 through Konsei Pass Tunnel
- Suganuma is immediately after tunnel exit, Marunuma beyond
Winter Notes:
Konsei Pass is typically closed seasonally from late November through late April of the following year. During this period, access from the Nikko side is impossible, so access must be via the Numata region. Additionally, winter snow and ice require studless tires or chains.
Parking Information
Suganuma:
- Suganuma Camp Village parking lot (for camp users)
- Multiple parking spaces along National Route
- Early arrival recommended during fall foliage season due to congestion
Marunuma:
- Parking lot near Marunuma Lakeside Pavilion
- Marunuma Highland Ski Area parking also available (may have fees depending on season)
Public Transportation Access
Public transportation access is limited and infrequent, so advance planning is essential.
Train/Rail:
- Get off at “Numata Station” on JR Joetsu Line
- Board Kanetsutsu Bus “Kamada/Daishimizu/Suganuma bound” (approximately 2 hours)
- Get off at “Marunuma” or “Suganuma” bus stop
Bus Notes:
- Very few buses run (several per day)
- Operating schedules may change seasonally
- Strongly recommended to confirm Kanetsutsu Bus timetable in advance
- Some routes may be suspended in winter
It’s a short walk from bus stops to each lake, but caution is needed if carrying heavy luggage or weather is poor.
Marunuma Highland Ski Area｜Winter Enjoyment
Ski Area Overview and Characteristics
Marunuma Highland Ski Area, located immediately near Marunuma, is a representative ski resort of Gunma Prefecture. Known for high altitude and good snow quality, it can be enjoyed for an extended season from season opening through spring skiing.
Ski Area Basic Information:
- Altitude: 1,400-2,000 meters
- Number of courses: 13
- Longest run: Approximately 4,000 meters
- Lifts: 6 (including gondola)
- Season: Early December-early May (varies by year)
Enjoying Spectacular Views via Nikko-Shirane Mountain Ropeway
One highlight of Marunuma Highland is the Nikko-Shirane Mountain Ropeway, which ascends to 2,000 meters in one go. In winter, it serves as ski/snowboard access; in green season (late May-early November), it operates as a sightseeing lift.
From the summit station, climbing Nikko-Shirane Mountain (2,578 meters), Honshu’s highest peak north of the Kanto region, is possible. Using the ropeway significantly reduces elevation gain. The views from near the summit are excellent, and on clear days, the gaze extends from Oze to Tanigawa-dake and even to Mount Fuji in the distance.
Green Season Activities
Summer at Marunuma Highland offers various activities utilizing the ski slopes.
- Trekking/Hiking: Alpine plant observation on maintained trails
- Summer Grass Slope: Artificial grass slope for skiing/snowboarding practice
- Mountain Biking: Thrilling downhill course experience
- Sky Footbath: Footbath at 2,000-meter summit station for relaxation while enjoying scenic views
Recommended Nearby Tourist Attractions
Konsei Pass and Konsei Tunnel
About 1km from Suganuma, Konsei Pass straddles the Gunma-Tochigi Prefecture border at 2,024 meters altitude. Once a treacherous pass route, the Konsei Tunnel (755 meters long) now enables safe passage. From the tunnel’s Gunma side entrance, spectacular views overlooking Suganuma spread out. The old pass trail is also accessible on foot, allowing history-infused hiking.
Katashina Village Hot Spring Facilities
Hot spring facilities dot the area within 30-40 minutes’ drive from Marunuma and Suganuma.
Major Hot Spring Facilities:
- Ojin Hot Springs: Katashina Village’s representative hot spring resort. Many facilities offer day-trip bathing
- Oze Iwakura Hot Springs: Hot spring within Oze Iwakura Resort Hotel. Famous for excellent views from open-air baths
- Katashina Highland Hot Springs: Known for beauty-enhancing mineral content
Enjoying hot springs after lake exploration or mountain climbing represents luxury unique to this region.
Oze National Park
Known as the “gateway to Oze,” Katashina Village provides access to Oze’s entry points within 40-60 minutes by car.
- Hatomatsu Pass: Most common entry point to Oze Wetland
- Daishimizu: Access route to Oze Lake
Oze represents Japan’s premier wetland, with cherry blossoms in late May, Japanese bistorta in July, and autumn grass color offering four-season spectacular views. Visiting alongside Marunuma and Suganuma allows full appreciation of Katashina Village’s natural appeal.
Fukiwari Waterfall
Called “Asia’s Niagara,” Fukiwari Waterfall, positioned toward Numata in Katashina Village, is a renowned cascade. About 50 minutes by car from Marunuma, the 30-meter-wide, 7-meter-high waterfall’s dramatic flow is impressive.
Well-maintained trails offer close waterfall observation, with suspension bridges and scenic gorge viewpoints abundant. During autumn foliage season, waterfall and foliage create magnificent collaboration.
Recommended Local Cuisine Information
Marunuma Lakeside Pavilion
Marunuma Lakeside Pavilion, standing on Marunuma’s shore, offers restaurant dining with lake views. Mountain vegetable soba, voluminous curry rice, light meals, and more using local ingredients are available.
Particularly recommended are soba made with Gunma-prefecture ingredients and hearty cutlet curry. Perfect for rest breaks during walks or roadside meals. Window-side seating provides panoramic Marunuma views, and dining while enjoying seasonal scenery is exceptional.
Katashina Village Soba Restaurants
Katashina Village, recognized as a soba-producing region utilizing pure water and cool climate, features hand-made soba restaurants within 20-30 minutes’ drive.
Ten-rin soba using locally-milled flour is fragrant with excellent throat-clearing quality. Combined with wild vegetable tempura, it fully showcases Katashina’s natural bounty.
Roadside Station “Oze Katashina”
Located in central Katashina Village, Roadside Station “Oze Katashina” sells fresh local agricultural products and specialties.
Recommended Products:
- Flower Beans: Katashina specialty large beans. Available as boiled beans or processed sweets
- Maitake Mushrooms: Gunma Prefecture is a major maitake producer. Fresh mushrooms and processed goods plentiful
- Apples/Blueberries: High-altitude cultivation yields high-sugar fruits
- Local Sake: Various Gunma Prefecture fine sake
An attached restaurant features popular vegetable buffet-style meals using Katashina produce.
Accommodation Options and Hotel Information
Hotels Around Marunuma Highland
Chalet Marunuma:
Resort hotel positioned on Marunuma Highland ski area slopes. Ideal as piste-side convenience in ski season and Marunuma/Suganuma sightseeing base during green season. Hot spring bath facility complete for relaxation.
Pension Area:
Family-operated pensions near Marunuma Highland offer warmth. Homemade meals and hospitable atmosphere attract repeat visitors.
Katashina Village Hot Spring Inns
Ojin Hot Spring Inns:
Historic hot springs line the Ojin Hot Spring resort area. Enjoy flowing hot springs and kaiseki meals featuring local ingredients. About 40 minutes’ drive from Marunuma/Suganuma.
Oze Iwakura Resort Hotel:
Large resort hotel adjacent Oze Iwakura Ski Area. Excellent hot spring facilities with renowned open-air bath views. Utilized as summer trekking/activity base and winter ski resort.
Campgrounds
Suganuma Camp Village:
As previously mentioned, located on Suganuma’s shore. Camping with lake views offers special experience. Bungalows available for tent-inexperienced guests.
Marunuma Auto Campground:
Near Marunuma. Pull-through hookups convenient for family camping with substantial gear. Shower facilities and cooking areas well-maintained.
Four-Season Enjoyment
Spring (May-June)
During snowmelt season, fresh greenery appears beautiful around Marunuma/Suganuma, with striking contrast against snow-capped Nikko-Shirane Mountain. Late May onward, Nikko-Shirane Mountain Ropeway opens for green season, enabling alpine plant observation.
Water irises and marsh marigolds reach prime viewing, making nature observation ideal. Fewer tourists allow quiet nature appreciation.
Summer (July-August)
High altitude keeps summer surprisingly cool. Average temperatures around 20 degrees Celsius provide ideal summer refuge. SUP and canoe activities peak, with transparent lake surfaces creating exhilarating experiences. Crowded campgrounds feature starlit nights.
Fall (September-October)
Marunuma/Suganuma’s most beautiful season is autumn foliage. Color begins late September, peaking early to mid-October. The reflected foliage on deep blue surfaces takes breath away, attracting photographers and tourists. Sharp morning/evening cold requires winter preparation. Misty early morning scenes create fantastical atmosphere.
Winter (November-April)
Late November brings Konsei Pass winter closure, blocking Nikko-area access. Marunuma Highland Ski Area opens early December with excellent snow quality for winter sports. While some Suganuma facilities close seasonally, frozen lake and snow-covered mountains create mystical scenery. However, snow/ice may restrict walking access; winter enjoyment centers on Marunuma Highland Ski Area.
Precautions and Etiquette for Visits
Natural Conservation Considerations
Marunuma/Suganuma sits within Nikko National Park, protecting valuable natural environments. Observe these precautions:
- Always remove trash: Never leave garbage on shores or trails
- No plant/animal collection: Protected by law; prohibited to collect alpine plants/insects
- Stay on designated areas: Don’t stray from trails to protect vegetation
- Fires only at designated sites: Absolutely prohibited outside campgrounds
Safety Measures
High altitude with changeable weather demands precautions:
- Prepare for sudden weather: Always carry rain gear/warm clothes
- Bear precautions: This is bear habitat. Carry bear bells, avoid solo hiking
- Cell phone signals: Limited reception in some areas
- Sunset time awareness: Plan with extra time; mountain sunset comes early
Facility Rules and Regulations
Campgrounds and facilities have specific usage rules. Confirm beforehand and follow rules. Peak periods (fall foliage/Golden Week) often require advance reservations; early planning recommended.
Conclusion｜Fully Enjoy Gunma Prefecture’s Great Nature at Marunuma and Suganuma
Marunuma and Suganuma in Katashina Village, Gunma Prefecture, offer enjoyment of two distinctive lakes: Suganuma boasting Honshu’s top transparency, and Marunuma displaying seasonal expressions. Located within Nikko National Park’s abundant natural environment, the high altitude provides cool climate, and convenient Kanto access add to its appeal.
Fall foliage spectacle, summer water activity refreshment, winter Marunuma Highland ski sports—varied year-round enjoyment awaits. Abundant surrounding attractions including Oze National Park, hot springs, and Fukiwari Waterfall support multi-day stays.
Experience Gunma Prefecture’s profound natural appeal at Marunuma and Suganuma. Why not visit and feel the beauty and tranquility? Perfect as weekend Kanto getaway or stopover toward Nagano/Hokkaido/Yamanashi.
