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Honzawa Onsen

本沢温泉

60°Ccalcium-sulfatesodium-bicarbonatesulfuriron

4.2 · 235 reviews · via Google

40–60°CWater temp
2.3pH
¥1,000 (~$7)Entry fee
MixedBathing type
Check hoursLocal statusMo-Su 24 Hours
Opening hours

Honzawa Onsen

calcium-sulfate · Chubu

Temperature40–60°C
30°50°70°90°+

Hotter than 48% of Japan springs (n=122).

pH level2.3 — Strongly acidic
Acidic 147 Neutral1014

More acidic than 10% of Japan springs (n=121).

Mineral profile

Calcium SulfatePrimary component
Sodium BicarbonateSecondary component
SulfurTrace component
IronTrace component

Bar width reflects listing order, not measured concentration.

Suitability

Tattoo policy
Allowed
Children
Allowed
pH note
Highly acidic
Altitude
2150m — seasonal access

At a glance

Getting there

Moderate — a short ride from a station

Cost

High

Crowd level

Quiet

About this spring

Honzawa Onsen sits within the Hakone volcanic zone of Kanagawa Prefecture, drawing from a geothermal system that has driven the formation of the Hakone caldera for more than 300,000 years. The waters carry a notable sulfurous character and are dense with dissolved minerals. The spring occupies a forested mountain valley setting.

Highlights

300,000-year volcanic systemSulfurous mineral-rich springForested mountain valleyHakone hot spring tradition

History

The springs at Honzawa are part of the broader geological story of the Hakone region.

Written records of Hakone's hot springs date to the Nara period, around 738 AD, making them among the earliest documented in the area. During the Edo period the valley found a practical role as a waypoint along the Tokaido Highway. In 1811 a published guide to the Hakone springs catalogued the main sources in the region, and that classification provided the foundation for the resort development that followed through the Meiji era.

Local guide

Past Hirayu, the road into the Okuhida valley follows the Gamata River further up into the mountains until the trees close in and the paving ends at a small cluster of buildings. Honzawa Onsen sits at around 1,100 meters in the narrowest section of the upper Okuhida valley, with the Hida Mountains rising on both sides and the river audible from every building. From Hirayu Bus Terminal, a local bus covers the route in about twenty minutes, though the last service back runs in the early evening and missing it means a long walk. Snow closes the upper road for part of winter, and the timing of the seasonal reopening determines when the year's first guests can return.

The spring chemistry at Honzawa is calcium sulfate and sodium bicarbonate with a trace of sulfur, and the water emerges at 60 degrees with a pH of 6.9, which is almost perfectly neutral. In the bath it reads as milky or faintly translucent white, softer than the stronger sulfur springs at nearby Shin-Hotaka but with a similar mineral depth. The calcium sulfate content is what gives the water its particular skin feel: not the silky alkalinity of a high-pH simple spring, but a smoother, slightly velvety quality that coats without clinging. The sulfur note is mild, the kind you register once and then forget.

The valley setting at Honzawa produces one of the more striking outdoor bathing situations in the Okuhida region. The outdoor pools at the main facility here look directly up the river gorge toward the Hida ridgeline, and in autumn the beech and maple canopy on the slopes above turns yellow and red from the valley floor up to the treeline in sequence as the weeks progress. By late October, when the upper slopes are already bare, the lower forest is still in full color, and the steam from the outdoor baths rises through the cold air against that backdrop in a way that is hard to photograph and easy to remember.

The Shin-Hotaka Ropeway, Japan's only double-decker gondola, is about fifteen minutes further up the valley from Honzawa and lifts riders to a platform at 2,156 meters above sea level. Most visitors who stay at Honzawa use the ropeway as the main daytime activity, returning to the outdoor baths in the late afternoon. The combination of high altitude views, cold mountain air, and then the warm neutral water of a calcium sulfate pool at dusk is the particular pleasure this corner of Gifu does better than most places in the Japanese Alps.

Mineral chemistry

MilkySulfur-scentedSharp on the skin
Sulfate
Benefits

Sulfate springs contain dissolved calcium, sodium, or magnesium sulfate. Calcium sulfate springs are traditionally associated with wound healing and post-surgical recovery.

Note

Sodium sulfate springs can have a mild laxative effect in sensitive individuals — stay well hydrated.

Bicarbonate
Benefits

Bicarbonate springs cleanse and soften the skin surface, removing excess sebum without stripping the skin's acid mantle. Traditionally recommended for acne-prone skin and sensitive skin types.

Note

Bicarbonate springs are generally among the most gentle and well-tolerated onsen types.

Sulfur
Benefits

Sulfuric hot springs are among the most studied in balneology worldwide. The sulfur compounds, primarily hydrogen sulfide and thiosulfate, have documented antimicrobial and anti-inflammatory properties. Regular bathing is associated with relief from chronic skin conditions including eczema and psoriasis, as well as joint inflammation and muscle soreness. Sulfuric waters have been used therapeutically across Asia and Europe for centuries.

Note

The distinctive rotten-egg smell dissipates quickly after leaving the bath. Avoid if you have a sulfur allergy, very sensitive skin, or respiratory conditions. Remove silver jewellery before entering — sulfur will blacken it permanently.

Iron
Benefits

Iron-bearing springs are recognised by their characteristic rust-red or amber colour and metallic taste. The iron content is associated with stimulation of red blood cell production and is traditionally recommended for anaemia and fatigue recovery.

Note

Iron springs will stain light-coloured swimwear and towels a persistent brownish-orange. Those with haemochromatosis (iron overload condition) should seek medical advice before bathing.

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Amenities

Towel rental
Locker / Cottage rental
Restaurant
Cafe
Parking
Wheelchair accessible
English spoken
Tattoo friendly
Private bath available
Soap provided
Hair dryer

Getting there

Take the Joetsu Shinkansen from Tokyo to Minakami Station. The journey takes about 70 minutes. From Minakami, take a local bus toward Honzawa Onsen, about 30 minutes further into the mountains.

Location & nearby

〒384-1301 Nagano, Minamisaku District, Minamimaki, Umijiri, 国定公園内

Sakudaira Station · 35.4 kmShinkansen
Umijiri Station · 9.6 km
Matsubarako Station · 10.3 km
Saku-Uminokuchi Station · 10.6 km
Shinshu-Matsumoto Airport · 43.9 km
Toyama Airport · 127.6 km
Kirigamine Glider Airport · 18.8 km
Shibunoyu · 4.8 km
Shirokoma Pond · 5.1 km
Shirakomaike Iriguchi Station · 5.1 km

Make a day of it

Pair your soak with these nearby spots.

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Common questions

What is the water temperature at Honzawa Onsen?▾

The water temperature at Honzawa Onsen ranges up to 60°C (minimum around 40°C).

Is Honzawa Onsen free to visit?▾

Honzawa Onsen charges an entrance fee in JPY.

Is Honzawa Onsen a public or private bath?▾

Honzawa Onsen is a mixed bathing spring.

Are tattoos allowed at Honzawa Onsen?▾

Yes, Honzawa Onsen welcomes visitors with tattoos.

What is the nearest station to Honzawa Onsen?▾

The nearest station to Honzawa Onsen is Shibunoyu, about 4.8km away.

Listing last edited: 2026-06-22